Merge r120507 to chromium 1132 branch.

Merge r120507 to chromium 1132 branch.

[chromium] Use SkBitmap in ImageLayerChromium
 https://bugs.webkit.org/show_bug.cgi?id=89134
Reviewed by Adrienne Walker.
GraphicsLayer::setContentsToImage(Image*) is called whenever an image layer's image is or might have changed.
In Chromium, this used to hang on to a RefPtr<WebCore::Image> until the compositor was ready to upload texture contents.
This is potentially a bit fishy since the Image itself might not be in exactly the same state when we get around
to uploading textures and it also creates a bad dependency from ImageLayerChromium on WebCore::Image.
This patch grabs the underlying SkBitmap in the setContentsTo call and passes that into ImageLayerChromium
instead. I've also removed the venerable but redundant PlatformImage concept since all of chromium's images are
skia bitmaps these days.
Covered by existing tests, particularly compositing/images/ and compositing/color-matching/.
* WebCore.gypi:
* platform/graphics/chromium/GraphicsLayerChromium.cpp:
(WebCore::GraphicsLayerChromium::setContentsToImage):
* platform/graphics/chromium/ImageLayerChromium.cpp:
(WebCore::ImageLayerTextureUpdater::updateTextureRect):
(WebCore::ImageLayerTextureUpdater::setBitmap):
(ImageLayerTextureUpdater):
(WebCore::ImageLayerChromium::ImageLayerChromium):
(WebCore::ImageLayerChromium::setBitmap):
(WebCore::ImageLayerChromium::update):
(WebCore::ImageLayerChromium::contentBounds):
(WebCore::ImageLayerChromium::drawsContent):
* platform/graphics/chromium/ImageLayerChromium.h:
(ImageLayerChromium):
* platform/graphics/chromium/PlatformImage.cpp: Removed.
* platform/graphics/chromium/PlatformImage.h: Removed.

TBR=jamesr@chromium.org
BUG=124321