Revert "Go back to using dual source blending for lcd src-over even with non-opaque color"

This reverts commit b54bdef86eb5cf63b94588afaa9197f49374a5f5.

Reason for revert: breaking some bots
Original change's description:
> Go back to using dual source blending for lcd src-over even with non-opaque color
> 
> This is change is currently still safe since earlier in Skia we are still requiring
> the dst to be opaque. The change is a workaround to spots where trying to read the
> dst to do in shader blending is failing for some reason. This also should give back
> a little performance since doing dual source blending should be better than shader
> blends.
> 
> Bug: chromium:732341
> Change-Id: I795f8a520f87f3fbf5d63a9509fbd9f394ea2b29
> Reviewed-on: https://skia-review.googlesource.com/19703
> Reviewed-by: Brian Salomon <bsalomon@google.com>
> Commit-Queue: Greg Daniel <egdaniel@google.com>

TBR=egdaniel@google.com,bsalomon@google.com

Change-Id: Ibb9bc1ef4ec5967dabcd62c81f62c0989c14fbb8
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:732341
Reviewed-on: https://skia-review.googlesource.com/19815
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
2 files changed