add local-matrix to shader::context

BUG=skia:
R=scroggo@google.com, dominikg@chromium.org

Author: reed@google.com

Review URL: https://codereview.chromium.org/263293005

git-svn-id: http://skia.googlecode.com/svn/trunk/src@14592 2bbb7eff-a529-9590-31e7-b0007b416f81
8 files changed