Adding setSurface public API method to SkDeferredCanvas

The purpose of this change is to provide an API that Blink 2D canvas layers can use
to install a new render target when recovering from a lost graphics context.

Review URL: https://codereview.chromium.org/15896005

git-svn-id: http://skia.googlecode.com/svn/trunk@9276 2bbb7eff-a529-9590-31e7-b0007b416f81
3 files changed