cc: Replace Region with SimpleEnclosedRegion for occlusion tracking

cc/trees/occlusion_tracker.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_TREES_OCCLUSION_TRACKER_H_
 #define CC_TREES_OCCLUSION_TRACKER_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
 #include "cc/base/cc_export.h"
-#include "cc/base/region.h"
+#include "cc/base/simple_enclosed_region.h"
 #include "cc/layers/layer_iterator.h"
 #include "ui/gfx/rect.h"
 
 namespace cc {
 class LayerImpl;
+class Region;
 class RenderSurfaceImpl;
 class Layer;
 class RenderSurface;
 
 // This class is used to track occlusion of layers while traversing them in a
 // front-to-back order. As each layer is visited, one of the methods in this
 // class is called to notify it about the current target surface. Then,
 // occlusion in the content space of the current layer may be queried, via
 // methods such as Occluded() and UnoccludedContentRect(). If the current layer
 // owns a RenderSurfaceImpl, then occlusion on that RenderSurfaceImpl may also
@@ skipping 29 matching lines @@
                                   const gfx::Transform& draw_transform) const;
 
   // Gives an unoccluded sub-rect of |content_rect| in the content space of the
   // render_target owned by the layer. Used when considering occlusion for a
   // contributing surface that is rendering into another target.
   gfx::Rect UnoccludedContributingSurfaceContentRect(
       const gfx::Rect& content_rect,
       const gfx::Transform& draw_transform) const;
 
   // Gives the region of the screen that is not occluded by something opaque.
-  Region ComputeVisibleRegionInScreen() const {
-    DCHECK(!stack_.back().target->parent());
-    return SubtractRegions(screen_space_clip_rect_,
-                           stack_.back().occlusion_from_inside_target);
-  }
+  Region ComputeVisibleRegionInScreen() const;
 
   void set_minimum_tracking_size(const gfx::Size& size) {
     minimum_tracking_size_ = size;
   }
 
   // The following is used for visualization purposes.
   void set_occluding_screen_space_rects_container(
       std::vector<gfx::Rect>* rects) {
     occluding_screen_space_rects_ = rects;
   }
   void set_non_occluding_screen_space_rects_container(
       std::vector<gfx::Rect>* rects) {
     non_occluding_screen_space_rects_ = rects;
   }
 
  protected:
   struct StackObject {
     StackObject() : target(0) {}
     explicit StackObject(const LayerType* target) : target(target) {}
     const LayerType* target;
-    Region occlusion_from_outside_target;
-    Region occlusion_from_inside_target;
+    SimpleEnclosedRegion occlusion_from_outside_target;
+    SimpleEnclosedRegion occlusion_from_inside_target;
   };
 
   // The stack holds occluded regions for subtrees in the
   // RenderSurfaceImpl-Layer tree, so that when we leave a subtree we may apply
   // a mask to it, but not to the parts outside the subtree.
   // - The first time we see a new subtree under a target, we add that target to
   // the top of the stack. This can happen as a layer representing itself, or as
   // a target surface.
   // - When we visit a target surface, we apply its mask to its subtree, which
   // is at the top of the stack.
@@ skipping 36 matching lines @@
 };
 
 #if !defined(COMPILER_MSVC)
 extern template class OcclusionTracker<Layer>;
 extern template class OcclusionTracker<LayerImpl>;
 #endif
 
 }  // namespace cc
 
 #endif  // CC_TREES_OCCLUSION_TRACKER_H_