Reland of Allow canvases to be GPU-accelerated in Workers

Reland of Allow canvases to be GPU-accelerated in Workers (patchset #1 id:1 of https://codereview.chromium.org/2323573002/ )

Reason for revert:
The failure that was the reason for the original revert is still happening, so this change was not the cause.  Reverting the revert...

Original issue's description:
> Revert of Allow canvases to be GPU-accelerated in Workers (patchset #5 id:80001 of https://codereview.chromium.org/2300633004/ )
>
> Reason for revert:
> This makes the following tests fail on Linux MSAN bot:
>
> virtual/gpu/fast/canvas/canvas-createImageBitmap-invalid-blob-in-workers.html
> virtual/display_list_2d_canvas/fast/canvas/canvas-createImageBitmap-invalid-blob-in-workers.html
>
> Build link:
> https://uberchromegw.corp.google.com/i/chromium.webkit/builders/WebKit%20Linux%20MSAN/builds/12091
>
> Original issue's description:
> > Allow canvases to be GPU-accelerated in Workers
> >
> > This change sets up a per-thread shared GPU context that is managed by
> > a thread-specific singleton SharedGpuContext.  This means that all 2D
> > contexts on a given worker will use the same context, which avoids
> > having to rely on mailboxes all the time.  Also this CL makes deep changes
> > to AcceleratedStaticBitmapImage in order to support the use of
> > the current thread's shared context, and it handles transfers
> > between threads in order to support the transferrable behavior of
> > ImageBitmap objects.
> >
> > BUG=593514
> >
> > Committed: https://crrev.com/83ac5ff37da4ea1c6d052649ccea46dd4bd453d6
> > Cr-Commit-Position: refs/heads/master@{#416929}
>
> TBR=kbr@chromium.org,haraken@chromium.org,junov@chromium.org
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=593514
>
> Committed: https://crrev.com/5235c5b0662c2553b0c10ebece983c04d00ebed6
> Cr-Commit-Position: refs/heads/master@{#417127}

TBR=kbr@chromium.org,haraken@chromium.org,lushnikov@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=593514
Committed: https://crrev.com/04f74a5b5283f1e38fcf21ed684267cd13053e02
Cr-Commit-Position: refs/heads/master@{#417284}

[Justin Novosad, 2016-09-08 14:19:44]

The CQ bit was checked by junov@chromium.org

[Justin Novosad, 2016-09-08 14:19:45]

Created Reland of Allow canvases to be GPU-accelerated in Workers

[commit-bot: I haz the power, 2016-09-08 14:20:11]

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, 2016-09-08 14:21:09]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-09-08 14:22:30]

Description was changed from

==========
Reland of Allow canvases to be GPU-accelerated in Workers (patchset #1 id:1 of
https://codereview.chromium.org/2323573002/ )

Reason for revert:
The failure that was the reason for the original revert is still happening, so
this change was not the cause.  Reverting the revert...

Original issue's description:
> Revert of Allow canvases to be GPU-accelerated in Workers (patchset #5
id:80001 of https://codereview.chromium.org/2300633004/ )
> 
> Reason for revert:
> This makes the following tests fail on Linux MSAN bot:
> 
> virtual/gpu/fast/canvas/canvas-createImageBitmap-invalid-blob-in-workers.html
>
virtual/display_list_2d_canvas/fast/canvas/canvas-createImageBitmap-invalid-blob-in-workers.html
> 
> Build link:
>
https://uberchromegw.corp.google.com/i/chromium.webkit/builders/WebKit%20Linu...
> 
> Original issue's description:
> > Allow canvases to be GPU-accelerated in Workers
> >
> > This change sets up a per-thread shared GPU context that is managed by
> > a thread-specific singleton SharedGpuContext.  This means that all 2D
> > contexts on a given worker will use the same context, which avoids
> > having to rely on mailboxes all the time.  Also this CL makes deep changes
> > to AcceleratedStaticBitmapImage in order to support the use of
> > the current thread's shared context, and it handles transfers
> > between threads in order to support the transferrable behavior of
> > ImageBitmap objects.
> >
> > BUG=593514
> >
> > Committed: https://crrev.com/83ac5ff37da4ea1c6d052649ccea46dd4bd453d6
> > Cr-Commit-Position: refs/heads/master@{#416929}
> 
> TBR=kbr@chromium.org,haraken@chromium.org,junov@chromium.org
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=593514
> 
> Committed: https://crrev.com/5235c5b0662c2553b0c10ebece983c04d00ebed6
> Cr-Commit-Position: refs/heads/master@{#417127}

TBR=kbr@chromium.org,haraken@chromium.org,lushnikov@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=593514
==========

to

==========
Reland of Allow canvases to be GPU-accelerated in Workers (patchset #1 id:1 of
https://codereview.chromium.org/2323573002/ )

Reason for revert:
The failure that was the reason for the original revert is still happening, so
this change was not the cause.  Reverting the revert...

Original issue's description:
> Revert of Allow canvases to be GPU-accelerated in Workers (patchset #5
id:80001 of https://codereview.chromium.org/2300633004/ )
>
> Reason for revert:
> This makes the following tests fail on Linux MSAN bot:
>
> virtual/gpu/fast/canvas/canvas-createImageBitmap-invalid-blob-in-workers.html
>
virtual/display_list_2d_canvas/fast/canvas/canvas-createImageBitmap-invalid-blob-in-workers.html
>
> Build link:
>
https://uberchromegw.corp.google.com/i/chromium.webkit/builders/WebKit%20Linu...
>
> Original issue's description:
> > Allow canvases to be GPU-accelerated in Workers
> >
> > This change sets up a per-thread shared GPU context that is managed by
> > a thread-specific singleton SharedGpuContext.  This means that all 2D
> > contexts on a given worker will use the same context, which avoids
> > having to rely on mailboxes all the time.  Also this CL makes deep changes
> > to AcceleratedStaticBitmapImage in order to support the use of
> > the current thread's shared context, and it handles transfers
> > between threads in order to support the transferrable behavior of
> > ImageBitmap objects.
> >
> > BUG=593514
> >
> > Committed: https://crrev.com/83ac5ff37da4ea1c6d052649ccea46dd4bd453d6
> > Cr-Commit-Position: refs/heads/master@{#416929}
>
> TBR=kbr@chromium.org,haraken@chromium.org,junov@chromium.org
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=593514
>
> Committed: https://crrev.com/5235c5b0662c2553b0c10ebece983c04d00ebed6
> Cr-Commit-Position: refs/heads/master@{#417127}

TBR=kbr@chromium.org,haraken@chromium.org,lushnikov@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=593514

Committed: https://crrev.com/04f74a5b5283f1e38fcf21ed684267cd13053e02
Cr-Commit-Position: refs/heads/master@{#417284}
==========

[commit-bot: I haz the power, 2016-09-08 14:22:31]

Patchset 1 (id:??) landed as
https://crrev.com/04f74a5b5283f1e38fcf21ed684267cd13053e02
Cr-Commit-Position: refs/heads/master@{#417284}