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

cc/trees/occlusion.cc

-// 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.
-
-#include "cc/trees/occlusion.h"
-
-#include "cc/base/math_util.h"
-#include "ui/gfx/rect.h"
-
-namespace cc {
-
-Occlusion::Occlusion() {
-}
-
-Occlusion::Occlusion(const gfx::Transform& draw_transform,
-                     const SimpleEnclosedRegion& occlusion_from_outside_target,
-                     const SimpleEnclosedRegion& occlusion_from_inside_target)
-    : draw_transform_(draw_transform),
-      occlusion_from_outside_target_(occlusion_from_outside_target),
-      occlusion_from_inside_target_(occlusion_from_inside_target) {
-}
-
-bool Occlusion::IsOccluded(const gfx::Rect& content_rect) const {
-  if (content_rect.IsEmpty())
-    return true;
-
-  if (occlusion_from_inside_target_.IsEmpty() &&
-      occlusion_from_outside_target_.IsEmpty()) {
-    return false;
-  }
-
-  // Take the ToEnclosingRect at each step, as we want to contain any unoccluded
-  // partial pixels in the resulting Rect.
-  gfx::Rect unoccluded_rect_in_target_surface =
-      MathUtil::MapEnclosingClippedRect(draw_transform_, content_rect);
-  DCHECK_LE(occlusion_from_inside_target_.GetRegionComplexity(), 1u);
-  DCHECK_LE(occlusion_from_outside_target_.GetRegionComplexity(), 1u);
-  // These subtract operations are more lossy than if we did both operations at
-  // once.
-  unoccluded_rect_in_target_surface.Subtract(
-      occlusion_from_inside_target_.bounds());
-  unoccluded_rect_in_target_surface.Subtract(
-      occlusion_from_outside_target_.bounds());
-
-  return unoccluded_rect_in_target_surface.IsEmpty();
-}
-
-}  // namespace cc