Merge 114791 - [chromium] Clip TransparencyWin to prevent OOM from large Skia canvas

Merge 114791 - [chromium] Clip TransparencyWin to prevent OOM from large Skia canvas
https://bugs.webkit.org/show_bug.cgi?id=84289

Reviewed by James Robinson.

Source/WebCore:

TransparencyWin will create a Skia canvas of whatever size is passed
in, even if the result will ultimately be clipped. Handle the clip
implicitly and try (in some cases) to create a smaller canvas. This
can happen due to RenderBox::paintBoxDecorations passing a paint rect
down of the entire element's size.

Modes with more complicated transforms (ScaleTransform, UnTransform)
are not handled yet.

Tests: TransparencyWin.ClippedKeepTransformNoLayer
       TransparencyWin.ClippedKeepTransformOpaqueCompositeLayer
       TransparencyWin.ClippedKeepTransformOpaqueWhiteLayer

* platform/graphics/chromium/TransparencyWin.cpp:
(WebCore::TransparencyWin::computeLayerSize):

Source/WebKit/chromium:

Add a test that would OOM if the layer wasn't clipped. Also, verify
that clipping the canvas doesn't shift pixels around incorrectly.

* tests/TransparencyWinTest.cpp:
(WebCore::testClippedLayerKeepTransform):
(WebCore):
(WebCore::TEST):


TBR=enne@google.com
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=115492