[Chromium] Expose didCommitCompositorFrame in WebWidgetClient.
https://bugs.webkit.org/show_bug.cgi?id=107325

Reviewed by James Robinson.

Add a notification on WebWidgetClient called when the compositor commits a frame.

* public/WebWidgetClient.h:
(WebWidgetClient):
(WebKit::WebWidgetClient::didCommitCompositorFrame):
* src/WebViewImpl.cpp:
(WebKit::WebViewImpl::didCommit):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@140495 268f45cc-cd09-0410-ab3c-d52691b4dbfc