Add testRunner.capturePixelsThen() method

Add testRunner.capturePixelsThen() method

This method is similar to displayAsyncThen(), but allows the caller
to get the captured pixel data.

This is to be used in repaint tests to produce the minimum repaint
baselines. This is useful to discover under-repaint bugs with the help
of repaint visualization in layout test results, and to estimate
over-repaints.

R=enne
TBR=dpranke

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=277540

[Dirk Pranke, 2014-06-03 01:27:03]

I defer this to enne@

[enne (OOO), 2014-06-05 22:19:04]

The idea and plumbing lgtm.  I don't know enough about v8 to review that part of
the code.

[Xianzhu, 2014-06-05 22:22:06]

On 2014/06/05 22:19:04, enne wrote:
> The idea and plumbing lgtm.  I don't know enough about v8 to review that part
of
> the code.

Thanks for review.

dpranke@ and abarth@ could you please take a look at the v8 related code in
test_runner.cc? Thanks.

[Xianzhu, 2014-06-07 05:27:04]

On 2014/06/05 22:22:06, Xianzhu wrote:
> On 2014/06/05 22:19:04, enne wrote:
> > The idea and plumbing lgtm.  I don't know enough about v8 to review that
part
> of
> > the code.
> 
> Thanks for review.
> 
> dpranke@ and abarth@ could you please take a look at the v8 related code in
> test_runner.cc? Thanks.

or rubber stamp :) ?

[jochen (gone - plz use gerrit), 2014-06-07 05:36:05]

On 2014/06/07 05:27:04, Xianzhu wrote:
> On 2014/06/05 22:22:06, Xianzhu wrote:
> > On 2014/06/05 22:19:04, enne wrote:
> > > The idea and plumbing lgtm.  I don't know enough about v8 to review that
> part
> > of
> > > the code.
> > 
> > Thanks for review.
> > 
> > dpranke@ and abarth@ could you please take a look at the v8 related code in
> > test_runner.cc? Thanks.
> 
> or rubber stamp :) ?

If you use a gin array buffer, it won't be possible to pass the resulting array
buffer to any web API.

You'll probably want to use WebArrayBuffer

[Xianzhu, 2014-06-07 16:36:10]

On 2014/06/07 05:36:05, jochen traveling until Jun 23 wrote:
> On 2014/06/07 05:27:04, Xianzhu wrote:
> > On 2014/06/05 22:22:06, Xianzhu wrote:
> > > On 2014/06/05 22:19:04, enne wrote:
> > > > The idea and plumbing lgtm.  I don't know enough about v8 to review that
> > part
> > > of
> > > > the code.
> > > 
> > > Thanks for review.
> > > 
> > > dpranke@ and abarth@ could you please take a look at the v8 related code
in
> > > test_runner.cc? Thanks.
> > 
> > or rubber stamp :) ?
> 
> If you use a gin array buffer, it won't be possible to pass the resulting
array
> buffer to any web API.
> 
> You'll probably want to use WebArrayBuffer

Changed to using WebArrayBuffer.

Actually my previous code just worked because I didn't use gin::ArrayBuffer to
pass the result, but just to access the internal buffer of the v8::ArrayBuffer
(which seems not allowed through v8 API unless the buffer is externalized).
Using WebArrayBuffer looks much better.

[Xianzhu, 2014-06-16 17:06:20]

The CQ bit was checked by wangxianzhu@chromium.org

[commit-bot: I haz the power, 2014-06-16 17:08:23]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/wangxianzhu@chromium.org/301243022/80001

[commit-bot: I haz the power, 2014-06-16 21:38:49]

Change committed as 277540