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

R=bsalomon@google.com

Author: robertphillips@google.com

Review URL: https://codereview.chromium.org/266203003

git-svn-id: http://skia.googlecode.com/svn/trunk@14586 2bbb7eff-a529-9590-31e7-b0007b416f81
7 files changed