cc: Enable non-opaque harware overlays.

cc/output/overlay_strategy_single_on_top.cc

Index: cc/output/overlay_strategy_single_on_top.cc
diff --git a/cc/output/overlay_strategy_single_on_top.cc b/cc/output/overlay_strategy_single_on_top.cc
index f55a4350d6a327c053669b89ab78ce97401dc0ed..30fd0174fc3aaec2a1611d707335d66261e0a8ac 100644
--- a/cc/output/overlay_strategy_single_on_top.cc
+++ b/cc/output/overlay_strategy_single_on_top.cc
@@ -7,10 +7,15 @@
 #include "cc/base/math_util.h"
 #include "cc/output/overlay_candidate_validator.h"
 #include "cc/quads/draw_quad.h"
+#include "ui/gfx/buffer_types.h"
 #include "ui/gfx/geometry/rect_conversions.h"
 
 namespace cc {
 

[reveman, 2017/03/16 04:57:34]

nit: remove blank line

[Daniele Castagna, 2017/03/16 05:04:20]

Done.

+namespace {
+const gfx::BufferFormat kOverlayFormatsWithAlpha[] = {

[reveman, 2017/03/16 04:57:34]

nit: add blank line before this

[Daniele Castagna, 2017/03/16 05:04:20]

Done.

+    gfx::BufferFormat::RGBA_8888, gfx::BufferFormat::BGRA_8888};
+}

[reveman, 2017/03/16 04:57:34]

nit: add blank line after this :)

[Daniele Castagna, 2017/03/16 05:04:20]

Done.

 OverlayStrategySingleOnTop::OverlayStrategySingleOnTop(
     OverlayCandidateValidator* capability_checker)
     : capability_checker_(capability_checker) {
@@ -34,6 +39,17 @@ bool OverlayStrategySingleOnTop::Attempt(
         // TODO(dcastagna): Remove this once drm platform supports transforms.
         candidate.transform == gfx::OVERLAY_TRANSFORM_NONE &&
         !OverlayCandidate::IsOccluded(candidate, quad_list->cbegin(), it)) {
+      // We currently reject quads with alpha that do not request alpha blending
+      // since the alpha channel might not be set to 1 and we're not disabling
+      // blending when scanning out.
+      // TODO(dcastagna): We should support alpha formats without blending using
+      // the opaque FB at scanout.
+      if (std::find(std::begin(kOverlayFormatsWithAlpha),
+                    std::end(kOverlayFormatsWithAlpha),
+                    candidate.format) != std::end(kOverlayFormatsWithAlpha) &&
+          it->shared_quad_state->blend_mode == SkBlendMode::kSrc)
+        continue;
+
       if (candidate.display_rect.size().GetArea() >
           best_candidate.display_rect.size().GetArea()) {
         best_candidate = candidate;