Result:
- clients can get a filtered version of an image without having to setup a temp drawing environment
- for some cases, the process is more efficient even than (deprecated) drawSprite, since there is no need to draw/copy the result
Impl:
- made Proxy virtual so we don't need to have an existing device to use it
This, in conjunction with LocalMatrixImageFilter, should allow us to simplify and optimize ApplyImageFilter() in cc/output/gl_renderer.cc
BUG=skia:
Review URL: https://codereview.chromium.org/1390913005
88d064d0e4