Use the GrCacheable ID to eliminate the need for notifications to GrGpuGL when textures and RTs are deleted.

Also, rename GrCacheable::getGenerationID() to getInstanceID() since it doesn't behave like other "generation" IDs.

R=jvanverth@google.com

Author: bsalomon@google.com

Review URL: https://codereview.chromium.org/376703009
8 files changed