GrCustomStage Renaming Part 2

GrSamplerState member rename
GrCustomStageUnitTest rename
some comment updates
Review URL: https://codereview.appspot.com/6771043

git-svn-id: http://skia.googlecode.com/svn/trunk@6078 2bbb7eff-a529-9590-31e7-b0007b416f81
28 files changed