Actually flush the path stencil transform when the matrix changes

Fixes many tests to match the master gm more closely. Examples of fixes:
mixed_xfermodes, strokes_poly, gradients_view_perspective, strokes_round,
... .

Total 58 differing results.

BUG=1479
R=bsalomon@google.com

Author: kkinnunen@nvidia.com

Review URL: https://chromiumcodereview.appspot.com/22176002

git-svn-id: http://skia.googlecode.com/svn/trunk@10529 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed