Cleanup DrawingBuffer::paintCompositingResultsToCanvas

Cleanup DrawingBuffer::paintCompositingResultsToCanvas

Remove the unnecessary copyTexture and use the value tracked by 
WebGLRenderingContext when restoring the framebuffer binding instead of
querying GL_FRAMEBUFFER_BINDING.

BUG=

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=178723

[hj.r.chung, 2014-07-21 00:35:50]

This is a simple cleanup patch. PTAL!

[hj.r.chung, 2014-07-21 00:35:52]

This is a simple cleanup patch. PTAL!

[Ken Russell (switch to Gerrit), 2014-07-22 02:00:30]

This looks good, but please do a full layout test run and make sure this doesn't
regress any WebGL-related tests like the printing tests in
printing/webgl-repeated-printing.html, etc.

[hj.r.chung, 2014-07-22 04:07:49]

On 2014/07/22 02:00:30, Ken Russell wrote:
> This looks good, but please do a full layout test run and make sure this
doesn't
> regress any WebGL-related tests like the printing tests in
> printing/webgl-repeated-printing.html, etc.

Thanks!
I triggered the trybots and manually checked on my Linux machine that there are
no 
regressions in the webgl related layout tests.

[Ken Russell (switch to Gerrit), 2014-07-22 18:32:45]

OK. LGTM

[hj.r.chung, 2014-07-23 02:07:50]

On 2014/07/22 18:32:45, Ken Russell wrote:
> OK. LGTM

Thank you!

[hj.r.chung, 2014-07-23 02:07:55]

The CQ bit was checked by heejin.r.chung@samsung.com

[commit-bot: I haz the power, 2014-07-23 02:08:33]

CQ is trying da patch. Follow status at

https://chromium-status.appspot.com/cq/heejin.r.chung@samsung.com/409483002/2...

[commit-bot: I haz the power, 2014-07-23 03:14:00]

Change committed as 178723