First step in pulling SkPicturePlayback & SkPictureRecord out of SkPicture

First step in pulling SkPicturePlayback & SkPictureRecord out of SkPicture

This CL begins the process of making SkPicturePlayback & SkPictureRecord independent of SkPicture. It just moves the PathHeap into SkPicture to get a feel for where all this is going to lead.

Some items of note:

SkTimedPicture (debugger/QT) should wind up being just an SkPicturePlayback-derived object.

All the flattening & unflattening should migrate out of SkPicturePlayback and into SkPicture.

SkPicture::initForPlayback should eventually become something just SkPictureRecorder::endRecording calls.

SkPicture is passed into SkPicturePlayback's & SkPictureRecord's constructors. SkPicturePlayback only
holds onto a "const SkPicture*". The SkPicturePlayback:: CreateFromStream & CreateFromBuffer methods pass a non-const
SkPicture* down the call stack.

BUG=skia:2315
R=reed@google.com

Author: robertphillips@google.com

Review URL: https://codereview.chromium.org/249453002

git-svn-id: http://skia.googlecode.com/svn/trunk@14341 2bbb7eff-a529-9590-31e7-b0007b416f81