Infrastructure changes to support pull saveLayers forward task

Infrastructure changes to support pull-saveLayers-forward task

This is split out of (First pass at pre-rendering saveLayers for GPU - https://codereview.chromium.org/261663003/). 

It mainly:

	Moves NeedsDeepCopy to somewhere more accessible (so GrPictureUtils.cpp can use it)
	Moves ComputeAccelDataKey somewhere more accessible (so GPUPicture test can use it)
	Adds unit test for picture saveLayer analysis (done in EXPERIMENTAL_optimize)
        Adds new fields to SaveLayerInfo that are needed to pull forward layers

Committed: http://code.google.com/p/skia/source/detail?r=14571

Committed: http://code.google.com/p/skia/source/detail?r=14586

[bsalomon, 2014-05-05 17:38:35]

lgtm

https://codereview.chromium.org/266203003/diff/1/src/gpu/GrPictureUtils.h
File src/gpu/GrPictureUtils.h (right):

https://codereview.chromium.org/266203003/diff/1/src/gpu/GrPictureUtils.h#new...
src/gpu/GrPictureUtils.h:43: bool    fIsNested;
maybe a depth integer value?

[robertphillips, 2014-05-05 17:59:47]

The CQ bit was checked by robertphillips@google.com

[commit-bot: I haz the power, 2014-05-05 18:00:04]

CQ is trying da patch. Follow status at
 https://skia-tree-status.appspot.com/cq/robertphillips@google.com/266203003/1

[commit-bot: I haz the power, 2014-05-05 18:06:18]

Change committed as 14571

[robertphillips, 2014-05-05 19:24:45]

This was reverted in r14578 due to breaking Android unit tests

[robertphillips, 2014-05-06 11:56:26]

The CQ bit was checked by robertphillips@google.com

[commit-bot: I haz the power, 2014-05-06 11:56:40]

CQ is trying da patch. Follow status at

https://skia-tree-status.appspot.com/cq/robertphillips@google.com/266203003/2...

[commit-bot: I haz the power, 2014-05-06 12:02:26]

Change committed as 14586

[mtklein, 2014-05-06 12:54:20]

On 2014/05/06 12:02:26, I haz the power (commit-bot) wrote:
> Change committed as 14586

:(  Valgrind says the new test is leaking:
http://108.170.220.120:10117/builders/Test-Ubuntu12-ShuttleA-GTX550Ti-x86_64-...