Make sure we use clear load op on GrOpsTask as often as possible.

With this change we are also removing the code in the Gr*OpsRenderPass which
will dynamically change the load op for given clear calls. The load is is
set at creation time.

Change-Id: I19f0f37bb38f790b11052953106e0492e6f9fc87
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/237425
Commit-Queue: Greg Daniel <egdaniel@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
8 files changed