annotatedInvalidationRects should be in format x,y,w,h

This fixes the FrameViewer json serialization of annotatedInvalidationRects.
This CL fixes the format from (x, y, maxX, maxY) to (x, y, width, height).

BUG=402033

Review URL: https://codereview.chromium.org/659003002

git-svn-id: svn://svn.chromium.org/blink/trunk@183829 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Plumb in flag to enable antialiased clipping in HTML 5 Canvas

Here is the OWP tracking bug: https://code.google.com/p/chromium/issues/detail?id=422984
Here is the link to the entry on the feature dashboard: https://www.chromestatus.com/features/4871530282483712

Currently canvas clips are not antialiased which differs what what other
browsers are doing and what the users expect. Skia supports antialiased clipping
but Skia's gpu backend (which is used for canvas) can be significantly slower
for concave clips. 

This CL starts surfacing the desired antialiased clipping behavior behind a flag
so developers can start assessing the capability. There is a lot more work that
needs to occur in Skia before we have a consistently good story for gpu-backed
antialiased clipping so we will not be ready to switch behaviors for a while.

BUG=crbug.com/7508
BUG=crbug.com/422984

junov: core & platform
dglazkov: Source/web & public/web

Review URL: https://codereview.chromium.org/652483003

git-svn-id: svn://svn.chromium.org/blink/trunk@183830 bbb929c8-8fbe-4397-9dbb-9b2b20218538