src/components/copresence/rpc/rpc_handler.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "components/copresence/rpc/rpc_handler.h"
   6
   7 #include "base/bind.h"
   8 #include "base/command_line.h"
   9 #include "base/guid.h"
  10 #include "base/logging.h"
  11 #include "base/strings/string_util.h"
  12 #include "base/strings/stringprintf.h"
  13
  14 // TODO(ckehoe): time.h includes windows.h, which #defines DeviceCapabilities
  15 // to DeviceCapabilitiesW. This breaks the pb.h headers below. For now,
  16 // we fix this with an #undef.
  17 #include "base/time/time.h"
  18 #if defined(OS_WIN)
  19 #undef DeviceCapabilities
  20 #endif
  21
  22 #include "components/copresence/copresence_switches.h"
  23 #include "components/copresence/handlers/directive_handler.h"
  24 #include "components/copresence/handlers/gcm_handler.h"
  25 #include "components/copresence/proto/codes.pb.h"
  26 #include "components/copresence/proto/data.pb.h"
  27 #include "components/copresence/proto/rpcs.pb.h"
  28 #include "components/copresence/public/copresence_constants.h"
  29 #include "components/copresence/public/copresence_delegate.h"
  30 #include "components/copresence/rpc/http_post.h"
  31 #include "net/http/http_status_code.h"
  32
  33 // TODO(ckehoe): Return error messages for bad requests.
  34
  35 namespace copresence {
  36
  37 using google::protobuf::MessageLite;
  38 using google::protobuf::RepeatedPtrField;
  39
  40 const char RpcHandler::kReportRequestRpcName[] = "report";
  41
  42 namespace {
  43
  44 const int kTokenLoggingSuffix = 5;
  45 const int kInvalidTokenExpiryTimeMs = 10 * 60 * 1000;  // 10 minutes.
  46 const int kMaxInvalidTokens = 10000;
  47 const char kRegisterDeviceRpcName[] = "registerdevice";
  48 const char kDefaultCopresenceServer[] =
  49     "https://www.googleapis.com/copresence/v2/copresence";
  50
  51 // UrlSafe is defined as:
  52 // '/' represented by a '_' and '+' represented by a '-'
  53 // TODO(rkc): Move this to the wrapper.
  54 std::string ToUrlSafe(std::string token) {
  55   base::ReplaceChars(token, "+", "-", &token);
  56   base::ReplaceChars(token, "/", "_", &token);
  57   return token;
  58 }
  59
  60
  61 // Logging
  62
  63 // Checks for a copresence error. If there is one, logs it and returns true.
  64 bool IsErrorStatus(const Status& status) {
  65   if (status.code() != OK) {
  66     LOG(ERROR) << "Copresence error code " << status.code()
  67                << (status.message().empty() ? "" : ": " + status.message());
  68   }
  69   return status.code() != OK;
  70 }
  71
  72 void LogIfErrorStatus(const util::error::Code& code,
  73                       const std::string& context) {
  74   LOG_IF(ERROR, code != util::error::OK)
  75       << context << " error " << code << ". See "
  76       << "cs/google3/util/task/codes.proto for more info.";
  77 }
  78
  79 // If any errors occurred, logs them and returns true.
  80 bool ReportErrorLogged(const ReportResponse& response) {
  81   bool result = IsErrorStatus(response.header().status());
  82
  83   // The Report fails or succeeds as a unit. If any responses had errors,
  84   // the header will too. Thus we don't need to propagate individual errors.
  85   if (response.has_update_signals_response())
  86     LogIfErrorStatus(response.update_signals_response().status(), "Update");
  87   if (response.has_manage_messages_response())
  88     LogIfErrorStatus(response.manage_messages_response().status(), "Publish");
  89   if (response.has_manage_subscriptions_response()) {
  90     LogIfErrorStatus(response.manage_subscriptions_response().status(),
  91                      "Subscribe");
  92   }
  93
  94   return result;
  95 }
  96
  97 const std::string LoggingStrForToken(const std::string& auth_token) {
  98   if (auth_token.empty())
  99     return "anonymous";
 100
 101   std::string token_suffix = auth_token.substr(
 102       auth_token.length() - kTokenLoggingSuffix, kTokenLoggingSuffix);
 103   return base::StringPrintf("token ...%s", token_suffix.c_str());
 104 }
 105
 106
 107 // Request construction
 108 // TODO(ckehoe): Move these into a separate file?
 109
 110 template <typename T>
 111 BroadcastScanConfiguration GetBroadcastScanConfig(const T& msg) {
 112   if (msg.has_token_exchange_strategy() &&
 113       msg.token_exchange_strategy().has_broadcast_scan_configuration()) {
 114     return msg.token_exchange_strategy().broadcast_scan_configuration();
 115   }
 116   return BROADCAST_SCAN_CONFIGURATION_UNKNOWN;
 117 }
 118
 119 scoped_ptr<DeviceState> GetDeviceCapabilities(const ReportRequest& request) {
 120   scoped_ptr<DeviceState> state(new DeviceState);
 121
 122   TokenTechnology* ultrasound =
 123       state->mutable_capabilities()->add_token_technology();
 124   ultrasound->set_medium(AUDIO_ULTRASOUND_PASSBAND);
 125   ultrasound->add_instruction_type(TRANSMIT);
 126   ultrasound->add_instruction_type(RECEIVE);
 127
 128   TokenTechnology* audible =
 129       state->mutable_capabilities()->add_token_technology();
 130   audible->set_medium(AUDIO_AUDIBLE_DTMF);
 131   audible->add_instruction_type(TRANSMIT);
 132   audible->add_instruction_type(RECEIVE);
 133
 134   return state.Pass();
 135 }
 136
 137 // TODO(ckehoe): We're keeping this code in a separate function for now
 138 // because we get a version string from Chrome, but the proto expects
 139 // an int64 version. We should probably change the version proto
 140 // to handle a more detailed version.
 141 ClientVersion* CreateVersion(const std::string& client,
 142                              const std::string& version_name) {
 143   ClientVersion* version = new ClientVersion;
 144
 145   version->set_client(client);
 146   version->set_version_name(version_name);
 147
 148   return version;
 149 }
 150
 151 void AddTokenToRequest(const AudioToken& token, ReportRequest* request) {
 152   TokenObservation* token_observation =
 153       request->mutable_update_signals_request()->add_token_observation();
 154   token_observation->set_token_id(ToUrlSafe(token.token));
 155
 156   TokenSignals* signals = token_observation->add_signals();
 157   signals->set_medium(token.audible ? AUDIO_AUDIBLE_DTMF
 158                                     : AUDIO_ULTRASOUND_PASSBAND);
 159   signals->set_observed_time_millis(base::Time::Now().ToJsTime());
 160 }
 161
 162 }  // namespace
 163
 164
 165 // Public functions.
 166
 167 RpcHandler::RpcHandler(CopresenceDelegate* delegate,
 168                        DirectiveHandler* directive_handler,
 169                        GCMHandler* gcm_handler,
 170                        const PostCallback& server_post_callback)
 171     : delegate_(delegate),
 172       directive_handler_(directive_handler),
 173       gcm_handler_(gcm_handler),
 174       server_post_callback_(server_post_callback),
 175       invalid_audio_token_cache_(
 176           base::TimeDelta::FromMilliseconds(kInvalidTokenExpiryTimeMs),
 177           kMaxInvalidTokens) {
 178     DCHECK(delegate_);
 179     DCHECK(directive_handler_);
 180     // |gcm_handler_| is optional.
 181
 182     if (server_post_callback_.is_null()) {
 183       server_post_callback_ =
 184           base::Bind(&RpcHandler::SendHttpPost, base::Unretained(this));
 185     }
 186
 187     if (gcm_handler_) {
 188       gcm_handler_->GetGcmId(
 189           base::Bind(&RpcHandler::RegisterGcmId, base::Unretained(this)));
 190     }
 191   }
 192
 193 RpcHandler::~RpcHandler() {
 194   // Do not use |directive_handler_| or |gcm_handler_| here.
 195   // They will already have been destructed.
 196   for (HttpPost* post : pending_posts_)
 197     delete post;
 198 }
 199
 200 void RpcHandler::SendReportRequest(scoped_ptr<ReportRequest> request,
 201                                    const std::string& app_id,
 202                                    const std::string& auth_token,
 203                                    const StatusCallback& status_callback) {
 204   DCHECK(request.get());
 205
 206   // Check that we have a "device" registered for this auth token.
 207   bool queue_request = true;
 208   const auto& registration = device_id_by_auth_token_.find(auth_token);
 209   if (registration == device_id_by_auth_token_.end()) {
 210     // Not registered.
 211     RegisterForToken(auth_token);
 212   } else if (!registration->second.empty()) {
 213     // Registration complete.
 214     queue_request = false;
 215   }
 216
 217   // We're not registered, or registration is in progress.
 218   if (queue_request) {
 219     pending_requests_queue_.push_back(new PendingRequest(
 220         request.Pass(), app_id, auth_token, status_callback));
 221     return;
 222   }
 223
 224   DVLOG(3) << "Sending ReportRequest to server.";
 225
 226   // If we are unpublishing or unsubscribing, we need to stop those publish or
 227   // subscribes right away, we don't need to wait for the server to tell us.
 228   ProcessRemovedOperations(*request);
 229
 230   request->mutable_update_signals_request()->set_allocated_state(
 231       GetDeviceCapabilities(*request).release());
 232
 233   AddPlayingTokens(request.get());
 234
 235   SendServerRequest(kReportRequestRpcName,
 236                     registration->second,
 237                     app_id,
 238                     auth_token,
 239                     request.Pass(),
 240                     // On destruction, this request will be cancelled.
 241                     base::Bind(&RpcHandler::ReportResponseHandler,
 242                                base::Unretained(this),
 243                                status_callback));
 244 }
 245
 246 void RpcHandler::ReportTokens(const std::vector<AudioToken>& tokens) {
 247   DCHECK(!tokens.empty());
 248
 249   if (device_id_by_auth_token_.empty()) {
 250     VLOG(2) << "Skipping token reporting because no device IDs are registered";
 251     return;
 252   }
 253
 254   // Construct the ReportRequest.
 255   ReportRequest request;
 256   for (const AudioToken& token : tokens) {
 257     if (invalid_audio_token_cache_.HasKey(ToUrlSafe(token.token)))
 258       continue;
 259     DVLOG(3) << "Sending token " << token.token << " to server under "
 260              << device_id_by_auth_token_.size() << " device ID(s)";
 261     AddTokenToRequest(token, &request);
 262   }
 263
 264   // Report under all active tokens.
 265   for (const auto& registration : device_id_by_auth_token_) {
 266     SendReportRequest(make_scoped_ptr(new ReportRequest(request)),
 267                       registration.first);
 268   }
 269 }
 270
 271
 272 // Private functions.
 273
 274 RpcHandler::PendingRequest::PendingRequest(scoped_ptr<ReportRequest> report,
 275                                            const std::string& app_id,
 276                                            const std::string& auth_token,
 277                                            const StatusCallback& callback)
 278     : report(report.Pass()),
 279       app_id(app_id),
 280       auth_token(auth_token),
 281       callback(callback) {}
 282
 283 RpcHandler::PendingRequest::~PendingRequest() {}
 284
 285 void RpcHandler::RegisterForToken(const std::string& auth_token) {
 286   DVLOG(2) << "Sending " << LoggingStrForToken(auth_token)
 287            << " registration to server.";
 288
 289   scoped_ptr<RegisterDeviceRequest> request(new RegisterDeviceRequest);
 290
 291   // Add a GCM ID for authenticated registration, if we have one.
 292   if (auth_token.empty() || gcm_id_.empty()) {
 293     request->mutable_push_service()->set_service(PUSH_SERVICE_NONE);
 294   } else {
 295     DVLOG(2) << "Registering GCM ID with " << LoggingStrForToken(auth_token);
 296     request->mutable_push_service()->set_service(GCM);
 297     request->mutable_push_service()->mutable_gcm_registration()
 298         ->set_device_token(gcm_id_);
 299   }
 300
 301   // Only identify as a Chrome device if we're in anonymous mode.
 302   // Authenticated calls come from a "GAIA device".
 303   if (auth_token.empty()) {
 304     Identity* identity =
 305         request->mutable_device_identifiers()->mutable_registrant();
 306     identity->set_type(CHROME);
 307     identity->set_chrome_id(base::GenerateGUID());
 308
 309     // Since we're generating a new "Chrome ID" here,
 310     // we need to make sure this isn't a duplicate registration.
 311     DCHECK_EQ(0u, device_id_by_auth_token_.count(std::string()))
 312         << "Attempted anonymous re-registration";
 313   }
 314
 315   bool gcm_pending = !auth_token.empty() && gcm_handler_ && gcm_id_.empty();
 316   SendServerRequest(
 317       kRegisterDeviceRpcName,
 318       // This will have the side effect of populating an empty device ID
 319       // for this auth token in the map. This is what we want,
 320       // to mark registration as being in progress.
 321       device_id_by_auth_token_[auth_token],
 322       std::string(),  // app ID
 323       auth_token,
 324       request.Pass(),
 325       base::Bind(&RpcHandler::RegisterResponseHandler,
 326                  // On destruction, this request will be cancelled.
 327                  base::Unretained(this),
 328                  auth_token,
 329                  gcm_pending));
 330 }
 331
 332 void RpcHandler::ProcessQueuedRequests(const std::string& auth_token) {
 333   // Track requests that are not on this auth token.
 334   ScopedVector<PendingRequest> still_pending_requests;
 335
 336   // If there is no device ID for this auth token, registration failed.
 337   bool registration_failed =
 338       (device_id_by_auth_token_.count(auth_token) == 0);
 339
 340   // We momentarily take ownership of all the pointers in the queue.
 341   // They are either deleted here or passed on to a new queue.
 342   for (PendingRequest* request : pending_requests_queue_) {
 343     if (request->auth_token == auth_token) {
 344       if (registration_failed) {
 345         request->callback.Run(FAIL);
 346       } else {
 347         SendReportRequest(request->report.Pass(),
 348                           request->app_id,
 349                           request->auth_token,
 350                           request->callback);
 351       }
 352       delete request;
 353     } else {
 354       // The request is on a different auth token.
 355       still_pending_requests.push_back(request);
 356     }
 357   }
 358
 359   // Only keep the requests that weren't processed.
 360   // All the pointers in the queue are now spoken for.
 361   pending_requests_queue_.weak_clear();
 362   pending_requests_queue_ = still_pending_requests.Pass();
 363 }
 364
 365 void RpcHandler::SendReportRequest(scoped_ptr<ReportRequest> request,
 366                                    const std::string& auth_token) {
 367   SendReportRequest(request.Pass(),
 368                     std::string(),
 369                     auth_token,
 370                     StatusCallback());
 371 }
 372
 373 // Store a GCM ID and send it to the server if needed. The constructor passes
 374 // this callback to the GCMHandler to receive the ID whenever it's ready.
 375 // It may be returned immediately, if the ID is cached, or require a server
 376 // round-trip. This ID must then be passed along to the copresence server.
 377 // There are a few ways this can happen for each auth token:
 378 //
 379 // 1. The GCM ID is available when we first register, and is passed along
 380 //    with the RegisterDeviceRequest.
 381 //
 382 // 2. The GCM ID becomes available after the RegisterDeviceRequest has
 383 //    completed. Then the loop in this function will invoke RegisterForToken()
 384 //    again to pass on the ID.
 385 //
 386 // 3. The GCM ID becomes available after the RegisterDeviceRequest is sent,
 387 //    but before it completes. In this case, the gcm_pending flag is passed
 388 //    through to the RegisterResponseHandler, which invokes RegisterForToken()
 389 //    again to pass on the ID. The loop here must skip pending registrations,
 390 //    as the device ID will be empty.
 391 //
 392 // TODO(ckehoe): Add tests for these scenarios.
 393 void RpcHandler::RegisterGcmId(const std::string& gcm_id) {
 394   gcm_id_ = gcm_id;
 395   if (!gcm_id.empty()) {
 396     for (const auto& registration : device_id_by_auth_token_) {
 397       const std::string& auth_token = registration.first;
 398       const std::string& device_id = registration.second;
 399       if (!auth_token.empty() && !device_id.empty())
 400         RegisterForToken(auth_token);
 401     }
 402   }
 403 }
 404
 405 void RpcHandler::RegisterResponseHandler(
 406     const std::string& auth_token,
 407     bool gcm_pending,
 408     HttpPost* completed_post,
 409     int http_status_code,
 410     const std::string& response_data) {
 411   if (completed_post) {
 412     int elements_erased = pending_posts_.erase(completed_post);
 413     DCHECK_GT(elements_erased, 0);
 414     delete completed_post;
 415   }
 416
 417   // Registration is no longer in progress.
 418   // If it was successful, we'll update below.
 419   device_id_by_auth_token_.erase(auth_token);
 420
 421   RegisterDeviceResponse response;
 422   if (http_status_code != net::HTTP_OK) {
 423     // TODO(ckehoe): Retry registration if appropriate.
 424     LOG(ERROR) << LoggingStrForToken(auth_token)
 425                << " device registration failed";
 426   } else if (!response.ParseFromString(response_data)) {
 427     LOG(ERROR) << "Invalid RegisterDeviceResponse:\n" << response_data;
 428   } else if (!IsErrorStatus(response.header().status())) {
 429     const std::string& device_id = response.registered_device_id();
 430     DCHECK(!device_id.empty());
 431     device_id_by_auth_token_[auth_token] = device_id;
 432     DVLOG(2) << LoggingStrForToken(auth_token)
 433              << " device registration successful. Id: " << device_id;
 434
 435     // If we have a GCM ID now, and didn't before, pass it on to the server.
 436     if (gcm_pending && !gcm_id_.empty())
 437       RegisterForToken(auth_token);
 438   }
 439
 440   // Send or fail requests on this auth token.
 441   ProcessQueuedRequests(auth_token);
 442 }
 443
 444 void RpcHandler::ReportResponseHandler(const StatusCallback& status_callback,
 445                                        HttpPost* completed_post,
 446                                        int http_status_code,
 447                                        const std::string& response_data) {
 448   if (completed_post) {
 449     int elements_erased = pending_posts_.erase(completed_post);
 450     DCHECK(elements_erased);
 451     delete completed_post;
 452   }
 453
 454   if (http_status_code != net::HTTP_OK) {
 455     if (!status_callback.is_null())
 456       status_callback.Run(FAIL);
 457     return;
 458   }
 459
 460   DVLOG(3) << "Received ReportResponse.";
 461   ReportResponse response;
 462   if (!response.ParseFromString(response_data)) {
 463     LOG(ERROR) << "Invalid ReportResponse";
 464     if (!status_callback.is_null())
 465       status_callback.Run(FAIL);
 466     return;
 467   }
 468
 469   if (ReportErrorLogged(response)) {
 470     if (!status_callback.is_null())
 471       status_callback.Run(FAIL);
 472     return;
 473   }
 474
 475   for (const MessageResult& result :
 476       response.manage_messages_response().published_message_result()) {
 477     DVLOG(2) << "Published message with id " << result.published_message_id();
 478   }
 479
 480   for (const SubscriptionResult& result :
 481       response.manage_subscriptions_response().subscription_result()) {
 482     DVLOG(2) << "Created subscription with id " << result.subscription_id();
 483   }
 484
 485   if (response.has_update_signals_response()) {
 486     const UpdateSignalsResponse& update_response =
 487         response.update_signals_response();
 488     DispatchMessages(update_response.message());
 489
 490     for (const Directive& directive : update_response.directive())
 491       directive_handler_->AddDirective(directive);
 492
 493     for (const Token& token : update_response.token()) {
 494       switch (token.status()) {
 495         case VALID:
 496           // TODO(rkc/ckehoe): Store the token in a |valid_token_cache_| with a
 497           // short TTL (like 10s) and send it up with every report request.
 498           // Then we'll still get messages while we're waiting to hear it again.
 499           VLOG(1) << "Got valid token " << token.id();
 500           break;
 501         case INVALID:
 502           DVLOG(3) << "Discarding invalid token " << token.id();
 503           invalid_audio_token_cache_.Add(token.id(), true);
 504           break;
 505         default:
 506           DVLOG(2) << "Token " << token.id() << " has status code "
 507                    << token.status();
 508       }
 509     }
 510   }
 511
 512   // TODO(ckehoe): Return a more detailed status response.
 513   if (!status_callback.is_null())
 514     status_callback.Run(SUCCESS);
 515 }
 516
 517 void RpcHandler::ProcessRemovedOperations(const ReportRequest& request) {
 518   // Remove unpublishes.
 519   if (request.has_manage_messages_request()) {
 520     for (const std::string& unpublish :
 521         request.manage_messages_request().id_to_unpublish()) {
 522       directive_handler_->RemoveDirectives(unpublish);
 523     }
 524   }
 525
 526   // Remove unsubscribes.
 527   if (request.has_manage_subscriptions_request()) {
 528     for (const std::string& unsubscribe :
 529         request.manage_subscriptions_request().id_to_unsubscribe()) {
 530       directive_handler_->RemoveDirectives(unsubscribe);
 531     }
 532   }
 533 }
 534
 535 void RpcHandler::AddPlayingTokens(ReportRequest* request) {
 536   const std::string& audible_token =
 537       directive_handler_->GetCurrentAudioToken(AUDIBLE);
 538   const std::string& inaudible_token =
 539       directive_handler_->GetCurrentAudioToken(INAUDIBLE);
 540
 541   if (!audible_token.empty())
 542     AddTokenToRequest(AudioToken(audible_token, true), request);
 543   if (!inaudible_token.empty())
 544     AddTokenToRequest(AudioToken(inaudible_token, false), request);
 545 }
 546
 547 void RpcHandler::DispatchMessages(
 548     const RepeatedPtrField<SubscribedMessage>& messages) {
 549   if (messages.size() == 0)
 550     return;
 551
 552   // Index the messages by subscription id.
 553   std::map<std::string, std::vector<Message>> messages_by_subscription;
 554   DVLOG(3) << "Dispatching " << messages.size() << " messages";
 555   for (const SubscribedMessage& message : messages) {
 556     for (const std::string& subscription_id : message.subscription_id()) {
 557       messages_by_subscription[subscription_id].push_back(
 558           message.published_message());
 559     }
 560   }
 561
 562   // Send the messages for each subscription.
 563   for (const auto& map_entry : messages_by_subscription) {
 564     // TODO(ckehoe): Once we have the app ID from the server, we need to pass
 565     // it in here and get rid of the app id registry from the main API class.
 566     const std::string& subscription = map_entry.first;
 567     const std::vector<Message>& messages = map_entry.second;
 568     delegate_->HandleMessages(std::string(), subscription, messages);
 569   }
 570 }
 571
 572 // TODO(ckehoe): Pass in the version string and
 573 // group this with the local functions up top.
 574 RequestHeader* RpcHandler::CreateRequestHeader(
 575     const std::string& client_name,
 576     const std::string& device_id) const {
 577   RequestHeader* header = new RequestHeader;
 578
 579   header->set_allocated_framework_version(CreateVersion(
 580       "Chrome", delegate_->GetPlatformVersionString()));
 581   if (!client_name.empty()) {
 582     header->set_allocated_client_version(
 583         CreateVersion(client_name, std::string()));
 584   }
 585   header->set_current_time_millis(base::Time::Now().ToJsTime());
 586   if (!device_id.empty())
 587     header->set_registered_device_id(device_id);
 588
 589   DeviceFingerprint* fingerprint = new DeviceFingerprint;
 590   fingerprint->set_platform_version(delegate_->GetPlatformVersionString());
 591   fingerprint->set_type(CHROME_PLATFORM_TYPE);
 592   header->set_allocated_device_fingerprint(fingerprint);
 593
 594   return header;
 595 }
 596
 597 template <class T>
 598 void RpcHandler::SendServerRequest(
 599     const std::string& rpc_name,
 600     const std::string& device_id,
 601     const std::string& app_id,
 602     const std::string& auth_token,
 603     scoped_ptr<T> request,
 604     const PostCleanupCallback& response_handler) {
 605   request->set_allocated_header(CreateRequestHeader(app_id, device_id));
 606   server_post_callback_.Run(delegate_->GetRequestContext(),
 607                             rpc_name,
 608                             delegate_->GetAPIKey(app_id),
 609                             auth_token,
 610                             make_scoped_ptr<MessageLite>(request.release()),
 611                             response_handler);
 612 }
 613
 614 void RpcHandler::SendHttpPost(net::URLRequestContextGetter* url_context_getter,
 615                               const std::string& rpc_name,
 616                               const std::string& api_key,
 617                               const std::string& auth_token,
 618                               scoped_ptr<MessageLite> request_proto,
 619                               const PostCleanupCallback& callback) {
 620   // Create the base URL to call.
 621   CommandLine* command_line = CommandLine::ForCurrentProcess();
 622   const std::string copresence_server_host =
 623       command_line->HasSwitch(switches::kCopresenceServer) ?
 624       command_line->GetSwitchValueASCII(switches::kCopresenceServer) :
 625       kDefaultCopresenceServer;
 626
 627   // Create the request and keep a pointer until it completes.
 628   HttpPost* http_post = new HttpPost(
 629       url_context_getter,
 630       copresence_server_host,
 631       rpc_name,
 632       api_key,
 633       auth_token,
 634       command_line->GetSwitchValueASCII(switches::kCopresenceTracingToken),
 635       *request_proto);
 636
 637   http_post->Start(base::Bind(callback, http_post));
 638   pending_posts_.insert(http_post);
 639 }
 640
 641 }  // namespace copresence