Add handling for instantiate failure up the call stack

The following two CLs were created via grep:
https://skia-review.googlesource.com/c/4929/ (Guard against instantiate & accessRenderTarget failures)
https://skia-review.googlesource.com/c/4961/ (Remove accessRenderTarget call in SkGpuDevice ctor)

This CL was created by running through all the tests and having instantiate fail so it catches up-stack failures to handle a null return.

BUG=665681,665500,665621

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4991

Change-Id: I6611eec8d36679123eef140538ee2526fb18628f
Reviewed-on: https://skia-review.googlesource.com/4991
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
9 files changed