Fix SkImageSource::filterBounds()

Previously SkImageSource::filterBounds() uses the default
SkImageFilter::onFilterNodeBounds() which returns the input rect.

Now override onFilterNodeBounds() in SkImageSource to return src
or dst rect (with transform applied).

Change-Id: I6681e1ba97affb09ef1ca5bc03b3d0f66c10f149
Reviewed-on: https://skia-review.googlesource.com/46741
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Mike Reed <reed@google.com>
3 files changed