Decrement SkCanvas::fDeferredSaveCount in doSave()

We're currently decrementing early in checkForDeferredSave(), but that
means we break the getSaveCount() invariant during willSave() dispatch.

Instead, we can defer to doSave(), until after willSave() is called.
This allows overriders to call getSaveCount().

R=reed@google.com,robertphillips@google.com

Review URL: https://codereview.chromium.org/1113603002
1 file changed