mix-blend-mode implementation for accelerated layers

cc/trees/occlusion_tracker.cc

 // Copyright 2012 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/trees/occlusion_tracker.h"
 
 #include <algorithm>
 
 #include "cc/base/math_util.h"
 #include "cc/debug/overdraw_metrics.h"
@@ skipping 215 matching lines @@
 
   RenderSurfaceType* surface = finished_target->render_surface();
 
   // Readbacks always happen on render targets so we only need to check
   // for readbacks here.
   bool target_is_only_for_copy_request =
       finished_target->HasCopyRequest() && LayerIsHidden(finished_target);
 
   // If the occlusion within the surface can not be applied to things outside of
   // the surface's subtree, then clear the occlusion here so it won't be used.
-  if (finished_target->mask_layer() ||
-      !SurfaceOpacityKnown(surface) ||
+  if (finished_target->mask_layer() || !SurfaceOpacityKnown(surface) ||
       surface->draw_opacity() < 1 ||
+      !finished_target->uses_default_blend_mode() ||
       target_is_only_for_copy_request ||
       finished_target->filters().HasFilterThatAffectsOpacity()) {
     stack_.back().occlusion_from_outside_target.Clear();
     stack_.back().occlusion_from_inside_target.Clear();
   } else if (!SurfaceTransformsToTargetKnown(surface)) {
     stack_.back().occlusion_from_inside_target.Clear();
     stack_.back().occlusion_from_outside_target.Clear();
   }
 }
 
@@ skipping 164 matching lines @@
   DCHECK_EQ(layer->render_target(), stack_.back().target);
   if (stack_.empty())
     return;
 
   if (!layer->DrawsContent())
     return;
 
   if (!LayerOpacityKnown(layer) || layer->draw_opacity() < 1)
     return;
 
+  if (!layer->uses_default_blend_mode())
+    return;
+
   if (LayerIsInUnsorted3dRenderingContext(layer))
     return;
 
   if (!LayerTransformsToTargetKnown(layer))
     return;
 
   Region opaque_contents = layer->VisibleContentOpaqueRegion();
   if (opaque_contents.IsEmpty())
     return;
 
@@ skipping 251 matching lines @@
   unoccluded_rect.Intersect(content_rect);
 
   return unoccluded_rect;
 }
 
 // Instantiate (and export) templates here for the linker.
 template class OcclusionTrackerBase<Layer, RenderSurface>;
 template class OcclusionTrackerBase<LayerImpl, RenderSurfaceImpl>;
 
 }  // namespace cc