Refactor ResourceManager into separate managers per resource type. BUG=angleproject:1639 Change-Id: I943f553cfb0e0feb57953770784b48e22fccc875 Reviewed-on: https://chromium-review.googlesource.com/423172 Commit-Queue: Geoff Lang <geofflang@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>