Reland of: cc: Add occlusion checker as a fixed view of occlusion tracker.

cc/trees/occlusion_checker.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_CHECKER_H_
+#define CC_TREES_OCCLUSION_CHECKER_H_
+
+#include "base/basictypes.h"
+#include "cc/base/cc_export.h"
+#include "cc/base/simple_enclosed_region.h"
+#include "ui/gfx/rect.h"
+#include "ui/gfx/transform.h"
+
+namespace cc {
+class LayerImpl;
+class Layer;
+template <typename LayerType>
+class OcclusionTracker;
+
+template <typename LayerType>

[danakj, 2014/09/09 15:14:39]

i don't see why this class is templated, can we remove that?

[vmpstr, 2014/09/09 21:56:56]

Makes sense, I went overzealous with making it look like OcclusionTracker.

+class CC_EXPORT OcclusionChecker {
+ public:
+  OcclusionChecker();
+
+  bool Occluded(const gfx::Rect& content_rect) const;
+
+ private:
+  friend class OcclusionTracker<LayerType>;
+  OcclusionChecker(const gfx::Transform& draw_transform,
+                   const SimpleEnclosedRegion& occlusion_from_outside_target,
+                   const SimpleEnclosedRegion& occlusion_from_inside_target);
+
+  gfx::Transform draw_transform_;
+  SimpleEnclosedRegion occlusion_from_outside_target_;
+  SimpleEnclosedRegion occlusion_from_inside_target_;
+};
+
+#if !defined(COMPILER_MSVC)
+extern template class OcclusionChecker<Layer>;
+extern template class OcclusionChecker<LayerImpl>;
+#endif
+
+}  // namespace cc
+
+#endif  // CC_TREES_OCCLUSION_CHECKER_H_