Clean up incorrect getter function names in WebGL related classes in blink: patch II

BUG=293775
TEST=tree

Review URL: https://chromiumcodereview.appspot.com/23694043

git-svn-id: svn://svn.chromium.org/blink/trunk@158047 bbb929c8-8fbe-4397-9dbb-9b2b20218538