Add hints for potential overlay promotion on android.

components/display_compositor/compositor_overlay_candidate_validator_android.cc

Index: components/display_compositor/compositor_overlay_candidate_validator_android.cc
diff --git a/components/display_compositor/compositor_overlay_candidate_validator_android.cc b/components/display_compositor/compositor_overlay_candidate_validator_android.cc
index 805dae3b917d7147b70e749309e068ab3518483e..3a58a1cb4001efb0c4f956ab0e1251a2edbf4bd5 100644
--- a/components/display_compositor/compositor_overlay_candidate_validator_android.cc
+++ b/components/display_compositor/compositor_overlay_candidate_validator_android.cc
@@ -7,8 +7,10 @@
 #include <memory>
 
 #include "base/memory/ptr_util.h"
+#include "cc/base/resource_id.h"
 #include "cc/output/overlay_processor.h"
 #include "cc/output/overlay_strategy_underlay.h"
+#include "gpu/command_buffer/client/gles2_interface.h"
 #include "ui/gfx/geometry/rect_conversions.h"
 
 namespace display_compositor {
@@ -34,6 +36,29 @@ void CompositorOverlayCandidateValidatorAndroid::CheckOverlaySupport(
 
   if (!candidates->empty()) {
     cc::OverlayCandidate& candidate = candidates->front();
+
+    // TODO(liberato): maybe we should notify by resource, not by quad.  while

[liberato (no reviews please), 2016/11/19 18:25:52]

this comment block is a little stale, sorry.  we now do report per-resource via
IsResourcePromotable.  It does not check if multiple quads refer to the same
resource, but that seems to be not too important.

[piman, 2016/11/23 00:37:25]

As long as we gracefully handle the case, it's ok I think - keeping in mind that
we can't trust the renderer not to send 2 quads referring to the same resource.

[liberato (no reviews please), 2016/12/01 20:59:11]

Acknowledged.

+    // multiple quads could share a resource, i think that would just make them
+    // all not overlayable.  we don't currently check for this, but we could.
+    // maybe 'is_backed_by_surface_texture' should move to the resource.
+    // TODO: should we send in a ResourceProvider here, so that it can ask if
+    // the resource is backed by a surface texture or not, rather than store it
+    // in the candidate?
+    if (candidate.is_backed_by_surface_texture) {
+      // This quad would be promoted if it were backed by a SurfaceView.  Since
+      // it isn't, we can't promote it.
+      promotable_resources_.insert(candidate.resource_id);
+      return;
+    }
+
+    // This quad will be promoted.  We clear the promotable set here, since we
+    // can only promote a single quad.  Otherwise, somebody might try to back
+    // one of the promotable quads with a SurfaceView, and either it or |quad|
+    // would have to fall back to a texture.
+    // We could re-insert |candidate.resource_id| back into the set, but the
+    // quad that refers to it won't be in the list anyway after promotion.
+    promotable_resources_.clear();
+
     candidate.display_rect =
         gfx::RectF(gfx::ToEnclosingRect(candidate.display_rect));
     candidate.overlay_handled = true;
@@ -50,4 +75,13 @@ bool CompositorOverlayCandidateValidatorAndroid::AllowCALayerOverlays() {
 void CompositorOverlayCandidateValidatorAndroid::SetSoftwareMirrorMode(
     bool enabled) {}
 
+void CompositorOverlayCandidateValidatorAndroid::ClearPromotableResources() {
+  promotable_resources_.clear();
+}
+
+bool CompositorOverlayCandidateValidatorAndroid::IsResourcePromotable(
+    cc::ResourceId resource_id) {
+  return promotable_resources_.count(resource_id) > 0;
+}
+
 }  // namespace display_compositor