Store the dst texture used by an XP in GrPipeline rather than in the XP.

This will allow the XP to be created before the dst texture.

Change-Id: I3e5bdfa8e5d47e58a3560792ce5cf3899d30a024
Reviewed-on: https://skia-review.googlesource.com/11011
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
20 files changed