Merge 120640 - [chromium] REGRESSION(r120346) ContentLayerPainter should clear rect to be painted

Merge 120640 - [chromium] REGRESSION(r120346) ContentLayerPainter should clear rect to be painted
https://bugs.webkit.org/show_bug.cgi?id=89376

Reviewed by Adrienne Walker.

In r120346, a refactor moved a clearRect()/clip() call from ContentLayerPainter - which all
ContentLayerChromiums use - out to OpaqueRectTrackingContentLayerDelegate - which all GraphicsLayerChromium
backed layers use, but which callers using WebContentLayer directly do not use. This meant that the canvas
wasn't cleared/clipped as WebContentLayerClient.h claimed it would be. This moves the clear and the clip
into CanvasLayerTextureUpdater which all paths use, including layers that don't use the ContentLayerPainter.

* platform/graphics/chromium/ContentLayerChromium.cpp:
(WebCore::ContentLayerPainter::paint):
* platform/graphics/chromium/OpaqueRectTrackingContentLayerDelegate.cpp:
(WebCore::OpaqueRectTrackingContentLayerDelegate::paintContents):

TBR=jamesr@google.com
BUG=132982
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=120771