[Chromium] Move createMessagePortChannel to Platform.h

[Chromium] Move createMessagePortChannel to Platform.h
https://bugs.webkit.org/show_bug.cgi?id=85764

Reviewed by Adam Barth.

Part of a refactoring series. See tracking bug 82948.

Source/Platform:

* Platform.gypi:
* chromium/public/Platform.h:
(WebKit):
(Platform):
(WebKit::Platform::createMessagePortChannel):
* chromium/public/WebMessagePortChannel.h: Added.
(WebKit):
(WebMessagePortChannel):
(WebKit::WebMessagePortChannel::~WebMessagePortChannel):
* chromium/public/WebMessagePortChannelClient.h: Added.
(WebKit):
(WebMessagePortChannelClient):
(WebKit::WebMessagePortChannelClient::~WebMessagePortChannelClient):

Source/WebKit/chromium:

* WebKit.gyp:
* public/WebMessagePortChannel.h:
* public/platform/WebKitPlatformSupport.h:
(WebKit):
(WebKit::WebKitPlatformSupport::injectIDBKeyIntoSerializedValue):
* src/PlatformMessagePortChannel.cpp:
(WebCore::PlatformMessagePortChannel::PlatformMessagePortChannel):
* src/PlatformMessagePortChannel.h:
* src/SharedWorkerRepository.cpp:
* src/WebSharedWorkerImpl.cpp:
* src/WebWorkerClientImpl.cpp:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@117204 268f45cc-cd09-0410-ab3c-d52691b4dbfc