Enable blend optimizations with instanced draws

Enable blend optimizations with instanced draws

Implements InstancedRendering::Batch::computePipelineOptimizations.
It was originally believed that blend optimizations could only hurt
performance by interfering with batching. But it turns out that:

(1) blend optimizations can significantly improve GPU-side performance
by avoiding dual source blending and/or dst copies, and

(2) blend optimizations can actually *facilitate* batching by
allowing opaque src and src_over draws to combine.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2120163002

[csmartdalton, 2016-07-03 17:31:48]

Description was changed from

==========
Enable blend optimizations with instanced draws

Implements InstancedRendering::Batch::computePipelineOptimizations.
It was originally believed that blend optimizations could only hurt
performance by interfering with batching. But it turns out that:

(1) blend optimizations can significantly improve GPU-side performance
by avoiding dual source blending and/or dst copies, and

(2) blend optimizations can actually *facilitate* batching by
allowing opaque src and src_over draws to combine.

BUG=skia:
==========

to

==========
Enable blend optimizations with instanced draws

Implements InstancedRendering::Batch::computePipelineOptimizations.
It was originally believed that blend optimizations could only hurt
performance by interfering with batching. But it turns out that:

(1) blend optimizations can significantly improve GPU-side performance
by avoiding dual source blending and/or dst copies, and

(2) blend optimizations can actually *facilitate* batching by
allowing opaque src and src_over draws to combine.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2120163002
==========

[csmartdalton, 2016-07-03 17:36:43]

csmartdalton@google.com changed reviewers:
+ bsalomon@google.com

[csmartdalton, 2016-07-03 17:36:43]

https://codereview.chromium.org/2120163002/diff/1/src/gpu/instanced/Instanced...
File src/gpu/instanced/InstancedRendering.cpp (left):

https://codereview.chromium.org/2120163002/diff/1/src/gpu/instanced/Instanced...
src/gpu/instanced/InstancedRendering.cpp:397: // later combine with a non-rect.
This comment was actually just about a bug, fixed here:
https://codereview.chromium.org/2120153002/

[csmartdalton, 2016-07-05 23:08:17]

Description was changed from

==========
Enable blend optimizations with instanced draws

Implements InstancedRendering::Batch::computePipelineOptimizations.
It was originally believed that blend optimizations could only hurt
performance by interfering with batching. But it turns out that:

(1) blend optimizations can significantly improve GPU-side performance
by avoiding dual source blending and/or dst copies, and

(2) blend optimizations can actually *facilitate* batching by
allowing opaque src and src_over draws to combine.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2120163002
==========

to

==========
Enable blend optimizations with instanced draws

Implements InstancedRendering::Batch::computePipelineOptimizations.
It was originally believed that blend optimizations could only hurt
performance by interfering with batching. But it turns out that:

(1) blend optimizations can significantly improve GPU-side performance
by avoiding dual source blending and/or dst copies, and

(2) blend optimizations can actually *facilitate* batching by
allowing opaque src and src_over draws to combine.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2120163002
==========

[csmartdalton, 2016-07-05 23:08:36]

Rolled into https://codereview.chromium.org/2066993003/