cc: Reject non-opaque fullscreen overlay candidates.

cc/output/overlay_strategy_fullscreen.cc

Index: cc/output/overlay_strategy_fullscreen.cc
diff --git a/cc/output/overlay_strategy_fullscreen.cc b/cc/output/overlay_strategy_fullscreen.cc
index 681611fa5f233f99094eb6656d8d12d8be93cfd8..7082441cf46cddd90dc433db66e6d30146b2a544 100644
--- a/cc/output/overlay_strategy_fullscreen.cc
+++ b/cc/output/overlay_strategy_fullscreen.cc
@@ -38,8 +38,14 @@ bool OverlayStrategyFullscreen::Attempt(
   if (front == quad_list->end())
     return false;
 
+  const DrawQuad* quad = *front;
+  if (quad->ShouldDrawWithBlending() ||
+      quad->shared_quad_state->opacity != 1.f ||
+      quad->shared_quad_state->blend_mode != SkBlendMode::kSrcOver)

[reveman, 2017/03/08 21:40:49]

what about SkBlendMode::kSrc? Android uses this when no blending is required.

[Daniele Castagna, 2017/03/13 02:09:19]

Just wanted to keep it consistent with the check we've had in
OverlayCandidate::FromDrawQuad so far.
Do you want to allow kSrc as a fullscreen overlay in this CL? What kind of
content can I use to test that?

[reveman, 2017/03/13 02:14:49]

Play store should be enough to test this I think. EXO sets the opaque properties
when it sees SRC blending but it still needs to leave blending as SRC to render
correctly.

[Daniele Castagna, 2017/03/13 02:24:04]

Play store uses kSrcOver, otherwise we'd reject it as overlay, while IIRC it
gets promoted to overlay today.
Let me check.

[Daniele Castagna, 2017/03/13 03:32:56]

Play Store is kSrcOver.

[reveman, 2017/03/13 11:58:12]

Android M or N? What's the format of the buffer? I don't remember the exact
situations where kSrc was used but I know it's common for Android to use RGBA
formats and just set blending to kSrc to have us avoid the alpha channel. That's
the reason we have this API:
https://cs.chromium.org/chromium/src/components/exo/surface.cc?l=395

Where is the SkBlendMode::kSrcOver overlay check before this change? I'm failing
to see how this would not be a regression compared to before.

+    return false;
+
   OverlayCandidate candidate;
-  if (!OverlayCandidate::FromDrawQuad(resource_provider, *front, &candidate)) {
+  if (!OverlayCandidate::FromDrawQuad(resource_provider, quad, &candidate)) {
     return false;
   }