Run mixedxfermodes GM through the pipe.

Pass the size of the GM to SkGPipeWriter.startRecording(), so that
calls to getDeviceSize() on the returned SkCanvas return a reasonable
result. This allows removing the flag to skip mixedxfermodes.

BUG=https://code.google.com/p/skia/issues/detail?id=1199

Review URL: https://codereview.chromium.org/13814023

git-svn-id: http://skia.googlecode.com/svn/trunk@8598 2bbb7eff-a529-9590-31e7-b0007b416f81
2 files changed