Adds local coords to GrEffect system.

Effects can ask the builder for local coords which may or may not be distinct from positions.

GrEffectStage tracks changes to relationship between pos and local coords.

GrGLEffectMatrix and GrSingleTextureEffect can use either pos or textures as intput coords

GrSimpleTextureEffect now allows for an explicit texture coords attribute.
Review URL: https://codereview.chromium.org/12531015

git-svn-id: http://skia.googlecode.com/svn/trunk@8264 2bbb7eff-a529-9590-31e7-b0007b416f81
53 files changed