2D canvas: fix shadow rendering with "copy" compositing mode.

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
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=184190

[dshwang, 2014-10-22 13:52:47]

dongseong.hwang@intel.com changed reviewers:
+ junov@chromium.org, schenney@chromium.org

[dshwang, 2014-10-22 13:52:47]

could you review?

[Justin Novosad, 2014-10-22 15:01:22]

On 2014/10/22 13:52:47, dshwang wrote:
> could you review?

lgtm.
This is a great test. If there are other pixels tests that are rendundant with
it, you should remove them (keep ref tests and text baseline tests, since those
are preferred).

[dshwang, 2014-10-22 15:19:29]

On 2014/10/22 15:01:22, junov wrote:
> On 2014/10/22 13:52:47, dshwang wrote:
> > could you review?
> 
> lgtm.
> This is a great test. If there are other pixels tests that are rendundant with
> it, you should remove them (keep ref tests and text baseline tests, since
those
> are preferred).

Thank you for review! There is not redundant tests after looking around. worth
to note that canvas-shadow-source-in.html is not redundant also because it tests
drawImage().

[dshwang, 2014-10-22 15:19:41]

The CQ bit was checked by dongseong.hwang@intel.com

[commit-bot: I haz the power, 2014-10-22 15:20:14]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/672593002/1

[commit-bot: I haz the power, 2014-10-22 15:25:16]

Committed patchset #1 (id:1) as 184190