Re-land: exo: Take blending into account when setting opaque property.

components/exo/surface.cc

Index: components/exo/surface.cc
diff --git a/components/exo/surface.cc b/components/exo/surface.cc
index 07e22f0b906029b002da992a7bb1c3960841fa26..c18dc2f1bd679e2c13200848b4ccff450bbc61c8 100644
--- a/components/exo/surface.cc
+++ b/components/exo/surface.cc
@@ -477,8 +477,7 @@ void Surface::CommitSurfaceHierarchy() {
     window_->layer()->SetBounds(
         gfx::Rect(window_->layer()->bounds().origin(), content_size_));
     window_->layer()->SetFillsBoundsOpaquely(
-        state_.alpha == 1.0f &&

[jbauman, 2016/06/27 20:51:41]

So if the blend mode is SkXfermode::kSrc_Mode then the alpha should be ignored?
And the opaque_region should always be empty if alpha is not 1.0?

[reveman, 2016/06/27 20:54:21]

We should probably define this as part of the alpha blending interface we added.
For now we can say that if the client sets alpha to less than 1 and opaque to
true then output is undefined.

-
+        state_.blend_mode == SkXfermode::kSrc_Mode ||
         state_.opaque_region.contains(
             gfx::RectToSkIRect(gfx::Rect(content_size_))));
   }