Remove parts of //cc we aren't using

cc/trees/occlusion.h

-// Copyright 2014 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_H_
-#define CC_TREES_OCCLUSION_H_
-
-#include <string>
-
-#include "base/basictypes.h"
-#include "cc/base/cc_export.h"
-#include "cc/base/simple_enclosed_region.h"
-#include "ui/gfx/geometry/rect.h"
-#include "ui/gfx/transform.h"
-
-namespace cc {
-
-class CC_EXPORT Occlusion {
- public:
-  Occlusion();
-  Occlusion(const gfx::Transform& draw_transform,
-            const SimpleEnclosedRegion& occlusion_from_outside_target,
-            const SimpleEnclosedRegion& occlusion_from_inside_target);
-  Occlusion GetOcclusionWithGivenDrawTransform(
-      const gfx::Transform& transform) const;
-
-  bool HasOcclusion() const;
-  bool IsOccluded(const gfx::Rect& content_rect) const;
-  gfx::Rect GetUnoccludedContentRect(const gfx::Rect& content_rect) const;
-
-  bool IsEqual(const Occlusion& other) const;
-  std::string ToString() const;
-
- private:
-  gfx::Rect GetUnoccludedRectInTargetSurface(
-      const gfx::Rect& content_rect) const;
-
-  gfx::Transform draw_transform_;
-  SimpleEnclosedRegion occlusion_from_outside_target_;
-  SimpleEnclosedRegion occlusion_from_inside_target_;
-};
-
-}  // namespace cc
-
-#endif  // CC_TREES_OCCLUSION_H_