Fix gpu blurring on platforms that "useDrawInsteadOfClear"

Platforms that "useDrawInsteadOfClear" take a different path in
GrRenderTargetContext::internalClear. The different path involves
a lot of comparisons of the drawn rect with the bounds of the RenderTarget. Since the RenderTargets are now deferred (and the instantiated version might be larger than the proxied size) case must be taken in prematurely optimizing away clears and draws.

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=5148

TBR=bsalomon@google.com

Change-Id: If63b6393fb66328175bc92de211e7242e903f25e
Reviewed-on: https://skia-review.googlesource.com/5148
Reviewed-by: Robert Phillips <robertphillips@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
9 files changed