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

cc/trees/occlusion_checker.h

Index: cc/trees/occlusion_checker.h
diff --git a/cc/trees/occlusion_checker.h b/cc/trees/occlusion_checker.h
new file mode 100644
index 0000000000000000000000000000000000000000..c4b809f23d75ae4884d9ba0f383812ce5d2380e6
--- /dev/null
+++ b/cc/trees/occlusion_checker.h
@@ -0,0 +1,41 @@
+// 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 CC_EXPORT OcclusionChecker {
+ public:
+  OcclusionChecker();
+  OcclusionChecker(const gfx::Transform& draw_transform,
+                   const SimpleEnclosedRegion& occlusion_from_outside_target,
+                   const SimpleEnclosedRegion& occlusion_from_inside_target);
+
+  bool Occluded(const gfx::Rect& content_rect);
+
+ private:
+  gfx::Transform draw_transform_;

[danakj, 2014/09/05 19:31:29]

This could really be part of the query, the rect + a transform from the rect to
the target. Saving the transform fixes the query space in place, which means
you'd have to map queries for each tiling into the same space, instead of giving
a transform modified by the tiling scale. Idk which is nicer.

[vmpstr, 2014/09/05 21:00:06]

I kind of prefer to have the occlusion checker fixed to be in a particular
space, and have the caller modify the query rect to that space. Otherwise, I
feel like it might get a bit messy.

+  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_