[PDF] Fix clipping in xfermode improvement.

[PDF] Fix clipping in xfermode improvement.

In some cases, the wrong clip (src clip instead of initial clip) was used.
Switch almost exclusively to initial clip because it is safe and generates a smaller result.

BUG=chromium:328009
Committed: http://code.google.com/p/skia/source/detail?r=12729

[vandebo (ex-Chrome), 2013-12-17 23:11:03]

https://codereview.chromium.org/116423004/diff/1/gm/xfermodes.cpp
File gm/xfermodes.cpp (right):

https://codereview.chromium.org/116423004/diff/1/gm/xfermodes.cpp#newcode117
gm/xfermodes.cpp:117: case kRectangleWithMask_SrcType: {
This demonstrates the problem in the bug before the fix.

https://codereview.chromium.org/116423004/diff/1/src/pdf/SkPDFDevice.cpp
File src/pdf/SkPDFDevice.cpp (left):

https://codereview.chromium.org/116423004/diff/1/src/pdf/SkPDFDevice.cpp#oldc...
src/pdf/SkPDFDevice.cpp:2008: ScopedContentEntry inShapeContentEntry(this,
&fExistingClipStack,
This was dead code - inShapeContentEntry is not used.

https://codereview.chromium.org/116423004/diff/1/src/pdf/SkPDFDevice.cpp#oldc...
src/pdf/SkPDFDevice.cpp:2011: if (!inShapeContentEntry.entry()) {
This can't be true because fExistingClipRegion is not empty and xfermode is
SrcOver.

[bungeman-skia, 2013-12-17 23:18:33]

lgtm

[commit-bot: I haz the power, 2013-12-17 23:25:45]

CQ is trying da patch. Follow status at
https://skia-tree-status.appspot.com/cq/vandebo@chromium.org/116423004/1

[commit-bot: I haz the power, 2013-12-17 23:38:32]

Change committed as 12729