cc: Reject non-opaque fullscreen overlay candidates.

cc/output/overlay_strategy_fullscreen.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/output/overlay_strategy_fullscreen.h"
 
 #include "cc/base/math_util.h"
 #include "cc/output/overlay_candidate_validator.h"
 #include "cc/quads/draw_quad.h"
 #include "cc/quads/solid_color_draw_quad.h"
@@ skipping 20 matching lines @@
   auto front = quad_list->begin();
   while (front != quad_list->end()) {
     if (!OverlayCandidate::IsInvisibleQuad(*front))
       break;
     front++;
   }
 
   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;
   }
 
   if (candidate.transform != gfx::OVERLAY_TRANSFORM_NONE) {
     return false;
   }
 
   if (!candidate.display_rect.origin().IsOrigin() ||
       gfx::ToRoundedSize(candidate.display_rect.size()) !=
           render_pass->output_rect.size() ||
       render_pass->output_rect.size() != candidate.resource_size_in_pixels) {
     return false;
   }
 
   candidate.plane_z_order = 0;
   candidate.overlay_handled = true;
   OverlayCandidateList new_candidate_list;
   new_candidate_list.push_back(candidate);
   capability_checker_->CheckOverlaySupport(&new_candidate_list);
   if (!new_candidate_list.front().overlay_handled)
     return false;
 
   candidate_list->swap(new_candidate_list);
 
   render_pass->quad_list = QuadList();  // Remove all the quads
   return true;
 }
 
 }  // namespace cc