Move Texture Serials to the base class. It's reasonable to use the serial logic on both the GL and all other translated Renderers, since we check the logic on the GL-side. Serials give us a way to identify Textures that aren't raw pointers and aren't "id". "id" has issues when Textures are deleted, then re-allocated with the same value. BUG=angle:781 Change-Id: I1a2a8b6f4ea3db915574c957c143a81e0210ec7d Reviewed-on: https://chromium-review.googlesource.com/222922 Tested-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Brandon Jones <bajones@chromium.org>