DevTools: replace mouseout with mouseleave where possible.

Review URL: https://codereview.chromium.org/669113002

git-svn-id: svn://svn.chromium.org/blink/trunk@184189 bbb929c8-8fbe-4397-9dbb-9b2b20218538
2D canvas: fix shadow rendering with "copy" compositing mode.

"copy" also needs temp layer, but we optimized it via clearing the canvas.
It's why we missed handling "copy" when we fix the bug related to shadow with "source-in".
This CL optimizes shadow with "copy" by not-drawing a shadow.

TEST=layout test fast/canvas/canvas-composite-shadow.html
BUG=417409

Review URL: https://codereview.chromium.org/672593002

git-svn-id: svn://svn.chromium.org/blink/trunk@184190 bbb929c8-8fbe-4397-9dbb-9b2b20218538