Fix a problem in the matrix convolution image filter exposed by https://code.google.com/p/skia/source/detail?r=7152:  when offsetting texture coordinates in a GrEffect, take the origin of the source bitmap origin into account, and flip Y coordinates when we need to.

NOTE:  this will cause the matrixconvolution GM's to need to be rebaselined (again!).

Review URL: https://codereview.appspot.com/7086054

git-svn-id: http://skia.googlecode.com/svn/trunk@7168 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed