In SKP serialization, use existing encoded data.

If an SkBitmap has encoded data, write that during serialization
rather than reencoding it.

Add a test to ensure that this does not modify the output stream,
so the reader need not know the difference.

Review URL: https://codereview.appspot.com/6884054

git-svn-id: http://skia.googlecode.com/svn/trunk@6732 2bbb7eff-a529-9590-31e7-b0007b416f81
3 files changed