Implement GL_VENDOR and GL_RENDERER strings for RendererGL. Change-Id: Ib83faa605fd1b992e19ddc2b72c7917d82245d32 Reviewed-on: https://chromium-review.googlesource.com/264664 Tested-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>