From 729b85ae8678ebd998a0e5f254817683198d0610 Mon Sep 17 00:00:00 2001
From: adamk <adamk@chromium.org>
Date: Tue, 31 Mar 2015 16:03:08 -0700
Subject: [PATCH] Add a UseCounter for Object.observe

It triggers once per context that calls observe (or attempts to access
any observation metadata, e.g. through Object.getNotifier).

Review URL: https://codereview.chromium.org/1048213002

Cr-Commit-Position: refs/heads/master@{#27557}
---
 include/v8.h                       |  1 +
 src/runtime/runtime-observe.cc     |  3 ++-
 test/cctest/test-object-observe.cc | 51 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 54 insertions(+), 1 deletion(-)

diff --git a/include/v8.h b/include/v8.h
index 19ba8e7..fd281ae 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -5146,6 +5146,7 @@ class V8_EXPORT Isolate {
     kMarkDequeOverflow = 3,
     kStoreBufferOverflow = 4,
     kSlotsBufferOverflow = 5,
+    kObjectObserve = 6,
     kUseCounterFeatureCount  // This enum value must be last.
   };
 
diff --git a/src/runtime/runtime-observe.cc b/src/runtime/runtime-observe.cc
index 211922c..a942645 100644
--- a/src/runtime/runtime-observe.cc
+++ b/src/runtime/runtime-observe.cc
@@ -88,8 +88,9 @@ RUNTIME_FUNCTION(Runtime_DeliverObservationChangeRecords) {
 
 
 RUNTIME_FUNCTION(Runtime_GetObservationState) {
-  SealHandleScope shs(isolate);
+  HandleScope scope(isolate);
   DCHECK(args.length() == 0);
+  isolate->CountUsage(v8::Isolate::kObjectObserve);
   return isolate->heap()->observation_state();
 }
 
diff --git a/test/cctest/test-object-observe.cc b/test/cctest/test-object-observe.cc
index 64634ad..50e2230 100644
--- a/test/cctest/test-object-observe.cc
+++ b/test/cctest/test-object-observe.cc
@@ -834,3 +834,54 @@ TEST(APIAccessorsShouldNotNotify) {
   CompileRun("Object.defineProperty(obj, 'accessor', { value: 44 });");
   CHECK(CompileRun("records")->IsNull());
 }
+
+
+namespace {
+
+int* global_use_counts = NULL;
+
+void MockUseCounterCallback(v8::Isolate* isolate,
+                            v8::Isolate::UseCounterFeature feature) {
+  ++global_use_counts[feature];
+}
+}
+
+
+TEST(UseCountObjectObserve) {
+  i::Isolate* isolate = CcTest::i_isolate();
+  i::HandleScope scope(isolate);
+  LocalContext env;
+  int use_counts[v8::Isolate::kUseCounterFeatureCount] = {};
+  global_use_counts = use_counts;
+  CcTest::isolate()->SetUseCounterCallback(MockUseCounterCallback);
+  CompileRun(
+      "var obj = {};"
+      "Object.observe(obj, function(){})");
+  CHECK_EQ(1, use_counts[v8::Isolate::kObjectObserve]);
+  CompileRun(
+      "var obj2 = {};"
+      "Object.observe(obj2, function(){})");
+  // Only counts the first use of observe in a given context.
+  CHECK_EQ(1, use_counts[v8::Isolate::kObjectObserve]);
+  {
+    LocalContext env2;
+    CompileRun(
+        "var obj = {};"
+        "Object.observe(obj, function(){})");
+  }
+  // Counts different contexts separately.
+  CHECK_EQ(2, use_counts[v8::Isolate::kObjectObserve]);
+}
+
+
+TEST(UseCountObjectGetNotifier) {
+  i::Isolate* isolate = CcTest::i_isolate();
+  i::HandleScope scope(isolate);
+  LocalContext env;
+  int use_counts[v8::Isolate::kUseCounterFeatureCount] = {};
+  global_use_counts = use_counts;
+  CcTest::isolate()->SetUseCounterCallback(MockUseCounterCallback);
+  CompileRun("var obj = {}");
+  CompileRun("Object.getNotifier(obj)");
+  CHECK_EQ(1, use_counts[v8::Isolate::kObjectObserve]);
+}
-- 
2.7.4