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

This reverts commit 7d6fe0b9964d139de64ca88c46d87eba41c7f84e.

Reason for revert: Relanding with fix

Original change's description:
> 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>

TBR=egdaniel@google.com,bsalomon@google.com
Bug: chromium:732341

Change-Id: I7481755a9aa64364371d8149af4458fc2c15c8aa
Reviewed-on: https://skia-review.googlesource.com/19840
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
2 files changed