Make SkAutoTMalloc's interface look more like SkAutoMalloc:
- add free(), which does what you expect
- make reset() return a pointer fPtr
No public API changes (SkAutoTMalloc is in include/private)
BUG=skia:2148
Review URL: https://codereview.chromium.org/1516833003
To avoid breaking existing SKPs, add a deserialization stub which
unflattens SkBitmapSource records to SkImageSources.
R=reed@google.com,mtklein@google.com,robertphillips@google.com
Review URL: https://codereview.chromium.org/1363913002