Rename GrPaint fields/enums/members texture->color mask->coverage.

R=robertphillips@google.com
Review URL: https://codereview.appspot.com/6615046

git-svn-id: http://skia.googlecode.com/svn/trunk@5827 2bbb7eff-a529-9590-31e7-b0007b416f81
9 files changed