Make OffscreenCanvas 2D context support globalAlpha

Make OffscreenCanvas 2D context support globalAlpha

We have already supported globalCompositeOperation, but globalAlpha is
not exposed yet.

This CL expose this attributes. Similar to the globalCompositeOperation,
the implementation is already there, we just need to expose it in the
.idl file.

The layout test is copied from fast/canvas/2d.composite.globalAlpha.fillPath.html,
with very small tweak.

BUG=659260
Committed: https://crrev.com/65114caf515dfa0d606a4189a7b10d65d51c8a7a
Cr-Commit-Position: refs/heads/master@{#435634}

[xidachen, 2016-11-23 14:22:55]

xidachen@chromium.org changed reviewers:
+ xlai@chromium.org

[xidachen, 2016-11-23 14:22:56]

PTAL

[xlai (Olivia), 2016-11-23 17:26:43]

https://codereview.chromium.org/2526693003/diff/1/third_party/WebKit/LayoutTe...
File
third_party/WebKit/LayoutTests/fast/canvas/OffscreenCanvas-2d-globalAlpha.html
(right):

https://codereview.chromium.org/2526693003/diff/1/third_party/WebKit/LayoutTe...
third_party/WebKit/LayoutTests/fast/canvas/OffscreenCanvas-2d-globalAlpha.html:14:
ctx.globalAlpha = 0.01; // avoid any potential alpha = 0 optimisations.
Could you use a more obvious number like 0.2, 0.7 etc for globalAlpha? Also,
include more globalAlpha values.

Also, could you use a reference test?

[xidachen, 2016-12-01 14:17:46]

xidachen@chromium.org changed reviewers:
+ junov@chromium.org
- xlai@chromium.org

[xidachen, 2016-12-01 14:17:46]

PTAL

[Justin Novosad, 2016-12-01 15:26:29]

lgtm

[xidachen, 2016-12-01 15:49:29]

The CQ bit was checked by xidachen@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-12-01 15:49:47]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[xidachen, 2016-12-01 17:00:53]

The CQ bit was unchecked by xidachen@chromium.org

[xidachen, 2016-12-01 17:01:03]

The CQ bit was checked by xidachen@chromium.org

[commit-bot: I haz the power, 2016-12-01 17:01:43]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-12-01 17:25:23]

CQ is committing da patch.

Bot data: {"patchset_id": 40001, "attempt_start_ts": 1480611663017100,
"parent_rev": "0a76bf8a0beba9374bfe54004db7498f0b2bb766", "commit_rev":
"28e6fbbc64bb81d6ff5f9e6f1667cf1ff3de3b54"}

[commit-bot: I haz the power, 2016-12-01 17:25:50]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2016-12-01 17:28:12]

Description was changed from

==========
Make OffscreenCanvas 2D context support globalAlpha

We have already supported globalCompositeOperation, but globalAlpha is
not exposed yet.

This CL expose this attributes. Similar to the globalCompositeOperation,
the implementation is already there, we just need to expose it in the
.idl file.

The layout test is copied from
fast/canvas/2d.composite.globalAlpha.fillPath.html,
with very small tweak.

BUG=659260
==========

to

==========
Make OffscreenCanvas 2D context support globalAlpha

We have already supported globalCompositeOperation, but globalAlpha is
not exposed yet.

This CL expose this attributes. Similar to the globalCompositeOperation,
the implementation is already there, we just need to expose it in the
.idl file.

The layout test is copied from
fast/canvas/2d.composite.globalAlpha.fillPath.html,
with very small tweak.

BUG=659260

Committed: https://crrev.com/65114caf515dfa0d606a4189a7b10d65d51c8a7a
Cr-Commit-Position: refs/heads/master@{#435634}
==========

[commit-bot: I haz the power, 2016-12-01 17:28:13]

Patchset 3 (id:??) landed as
https://crrev.com/65114caf515dfa0d606a4189a7b10d65d51c8a7a
Cr-Commit-Position: refs/heads/master@{#435634}