[GPU] Use view matrix + rect to implement subrect for drawBitmap when there is a mask filter and bleed.

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

Author: bsalomon@google.com

Review URL: https://codereview.chromium.org/65133003

git-svn-id: http://skia.googlecode.com/svn/trunk@12368 2bbb7eff-a529-9590-31e7-b0007b416f81
I feel like my clang is especially sensitive to unused variables.

BUG=

Review URL: https://codereview.chromium.org/82913006

git-svn-id: http://skia.googlecode.com/svn/trunk@12369 2bbb7eff-a529-9590-31e7-b0007b416f81