Implement GL_EXT_debug_marker for RendererGL. Passes dEQP-GLES2.functional.debug_marker.* Change-Id: I37f2b6724f32867d2e428613b1b6d9c8377c6d60 Reviewed-on: https://chromium-review.googlesource.com/302990 Reviewed-by: Corentin Wallez <cwallez@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org> Tested-by: Geoff Lang <geofflang@chromium.org>