cc: Make occlusion a draw property.

cc/layers/draw_properties.h

 // 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.
 
 #ifndef CC_LAYERS_DRAW_PROPERTIES_H_
 #define CC_LAYERS_DRAW_PROPERTIES_H_
 
 #include "base/memory/scoped_ptr.h"
+#include "cc/trees/occlusion.h"
 #include "third_party/skia/include/core/SkXfermode.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/transform.h"
 
 namespace cc {
 
 // Container for properties that layers need to compute before they can be
 // drawn.
 template <typename LayerType>
 struct CC_EXPORT DrawProperties {
@@ skipping 24 matching lines @@
         page_scale_factor(0.f),
         device_scale_factor(0.f) {}
 
   // Transforms objects from content space to target surface space, where
   // this layer would be drawn.
   gfx::Transform target_space_transform;
 
   // Transforms objects from content space to screen space (viewport space).
   gfx::Transform screen_space_transform;
 
+  // Known occlusion above the layer mapped to the content space of the layer.
+  Occlusion occlusion_in_content_space;
+
   // DrawProperties::opacity may be different than LayerType::opacity,
   // particularly in the case when a RenderSurface re-parents the layer's
   // opacity, or when opacity is compounded by the hierarchy.
   float opacity;
 
   // DrawProperties::blend_mode may be different than LayerType::blend_mode,
   // when a RenderSurface re-parents the layer's blend_mode.
   SkXfermode::Mode blend_mode;
 
   // xxx_is_animating flags are used to indicate whether the DrawProperties
@@ skipping 85 matching lines @@
   // have page scale applied and others not, this may differ between layers.
   float page_scale_factor;
 
   // The device scale factor that is applied to the layer.
   float device_scale_factor;
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_DRAW_PROPERTIES_H_