Add a layout test for potential bug on drawing video on SkCanvas

When drawing video frame on SkCanvas, chromium reuse the same cached SkBitmap
on both software SkCanvas and accelerated SkCanvas. After SkBitmap is used on
both SkCanvas, SkBitmap includes both GrTexture and system memory buffer. It's
weird and looks error-prone. Fortunately, it works now.
This CL adds new layout test to check if it will be broken. This potential bug is
fixed in https://codereview.chromium.org/662033002/

TEST=fast/canvas/yuv-video-on-accelerated-canvas.html
BUG=424591

Review URL: https://codereview.chromium.org/656683007

git-svn-id: svn://svn.chromium.org/blink/trunk@184073 bbb929c8-8fbe-4397-9dbb-9b2b20218538
The link shoud be activated by enter key on focusing the child element inside the anchor.
This makes behaviour consistent with firefox and IE.

BUG=350738
R=pdr@chromium.org
TEST=LayoutTests/fast/events/keydown-enter-key-on-focused-element-inside-link.html

Review URL: https://codereview.chromium.org/619613005

git-svn-id: svn://svn.chromium.org/blink/trunk@184074 bbb929c8-8fbe-4397-9dbb-9b2b20218538