[Chromium] Add profiling trace for deferred canvas rendering

[Chromium] Add profiling trace for deferred canvas rendering
https://bugs.webkit.org/show_bug.cgi?id=79376

Patch by Justin Novosad <junov@chromium.org> on 2012-02-23
Reviewed by Stephen White.

No new tests.

* platform/graphics/chromium/Canvas2DLayerChromium.cpp:
(WebCore::Canvas2DLayerChromium::paintContentsIfDirty):
Profiling trace for the entire method, as well as for
calls to canvas flush and context flush, both of which may
cause deferred operation to be executed.
* platform/graphics/skia/PlatformContextSkia.cpp:
(WebCore::PlatformContextSkia::bitmap):
Inserting a profiling trace in this method because it may cause
deferred draw commands to be executed.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@108714 268f45cc-cd09-0410-ab3c-d52691b4dbfc