Remove parts of //cc we aren't using

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/simple_enclosed_region.h"
-#include "cc/layers/layer_iterator.h"
-#include "cc/trees/occlusion.h"
-#include "ui/gfx/geometry/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
-// Occlusion from GetCurrentOcclusionForLayer(). If the current layer owns a
-// RenderSurfaceImpl, then occlusion on that RenderSurfaceImpl may also be
-// queried via surfaceOccluded() and surfaceUnoccludedContentRect(). Finally,
-// once finished with the layer, occlusion behind the layer should be marked by
-// calling MarkOccludedBehindLayer().
-template <typename LayerType>
-class CC_EXPORT OcclusionTracker {
- public:
-  explicit OcclusionTracker(const gfx::Rect& screen_space_clip_rect);
-  ~OcclusionTracker();
-
-  // Return an occlusion that retains the current state of the tracker
-  // and can be used outside of a layer walk to check occlusion.
-  Occlusion GetCurrentOcclusionForLayer(
-      const gfx::Transform& draw_transform) const;
-  Occlusion GetCurrentOcclusionForContributingSurface(
-      const gfx::Transform& draw_transform) const;
-
-  // Called at the beginning of each step in the LayerIterator's front-to-back
-  // traversal.
-  void EnterLayer(const LayerIteratorPosition<LayerType>& layer_iterator);
-  // Called at the end of each step in the LayerIterator's front-to-back
-  // traversal.
-  void LeaveLayer(const LayerIteratorPosition<LayerType>& layer_iterator);
-
-  // Gives the region of the screen that is not occluded by something opaque.
-  Region ComputeVisibleRegionInScreen() const;
-
-  void set_minimum_tracking_size(const gfx::Size& size) {
-    minimum_tracking_size_ = size;
-  }
-
- protected:
-  struct StackObject {
-    StackObject() : target(0) {}
-    explicit StackObject(const LayerType* target) : target(target) {}
-    const LayerType* 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.
-  // - When we visit a layer representing itself, we add its occlusion to the
-  // current subtree, which is at the top of the stack.
-  // - When we visit a layer representing a contributing surface, the current
-  // target will never be the top of the stack since we just came from the
-  // contributing surface.
-  // We merge the occlusion at the top of the stack with the new current
-  // subtree. This new target is pushed onto the stack if not already there.
-  std::vector<StackObject> stack_;
-
- private:
-  // Called when visiting a layer representing itself. If the target was not
-  // already current, then this indicates we have entered a new surface subtree.
-  void EnterRenderTarget(const LayerType* new_target);
-
-  // Called when visiting a layer representing a target surface. This indicates
-  // we have visited all the layers within the surface, and we may perform any
-  // surface-wide operations.
-  void FinishedRenderTarget(const LayerType* finished_target);
-
-  // Called when visiting a layer representing a contributing surface. This
-  // indicates that we are leaving our current surface, and entering the new
-  // one. We then perform any operations required for merging results from the
-  // child subtree into its parent.
-  void LeaveToRenderTarget(const LayerType* new_target);
-
-  // Add the layer's occlusion to the tracked state.
-  void MarkOccludedBehindLayer(const LayerType* layer);
-
-  gfx::Rect screen_space_clip_rect_;
-  gfx::Size minimum_tracking_size_;
-
-  DISALLOW_COPY_AND_ASSIGN(OcclusionTracker);
-};
-
-#if !defined(COMPILER_MSVC)
-extern template class OcclusionTracker<Layer>;
-extern template class OcclusionTracker<LayerImpl>;
-#endif
-
-}  // namespace cc
-
-#endif  // CC_TREES_OCCLUSION_TRACKER_H_