Code refactoring for getters and setters. The entry point should call into Context at first for getters and setters. BUG=angleproject:1922 Change-Id: Ibc8f726298cf334a6dafd6402e39c4dcd7e6d333 Reviewed-on: https://chromium-review.googlesource.com/450028 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>