Store GrRenderTarget in GrGpuCommandBuffer

Change-Id: I545d53ffb5f9d450b87a360516b03bdd47232a70
Reviewed-on: https://skia-review.googlesource.com/32460
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
17 files changed