Alter GrSurface/GrSurfaceProxy flags to prepare for GrTexture/GrTextureProxy -specific flags

This CL:
  moves GrRenderTarget::fFlags to GrSurface::fSurfaceFlags
  adds a GrInternalSurfaceFlags type and uses it for GrSurfaceProxy::fSurfaceFlags

  The goal of this is to provide a location where GrTexture/GrTextureProxy-specific flags
(i.e., isExternal & isRectangle) can be stored.

Change-Id: I8df7b79036a6853dd378ff6cf10d4b37c60dd511
Reviewed-on: https://skia-review.googlesource.com/114796
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
34 files changed