This test suite was missing the "GL_" prefix on some of the extension checks. This was causing every test in the suite to be skipped. Fix the check and also add some sanity checks that should ensure we expose certain extensions on particular platforms and renderers. Was discovered while working on changing the egl::Image class. Bug: angleproject:2714 Change-Id: Ida89b5c3c33c534e60cbd55c7e1117a6ef6faae9 Reviewed-on: https://chromium-review.googlesource.com/1142963Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>