cc: Make visible rect computation aware of pixel-moving filters

cc/trees/clip_expander.cc

Index: cc/trees/clip_expander.cc
diff --git a/cc/trees/clip_expander.cc b/cc/trees/clip_expander.cc
new file mode 100644
index 0000000000000000000000000000000000000000..84626ddb6b3cd503fef0a50eafc6763defabc529
--- /dev/null
+++ b/cc/trees/clip_expander.cc
@@ -0,0 +1,56 @@
+// Copyright 2016 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/clip_expander.h"
+#include "cc/trees/effect_node.h"
+#include "cc/trees/property_tree.h"
+#include "ui/gfx/transform.h"
+
+namespace cc {
+
+ClipExpander::ClipExpander(ExpanderType type, int filter_effect_id)
+    : expander_type_(type), target_effect_id_(filter_effect_id) {}
+
+ClipExpander::ClipExpander(const ClipExpander& other) = default;
+
+bool ClipExpander::operator==(const ClipExpander& other) const {
+  return expander_type_ == other.expander_type_ &&
+         target_effect_id_ == other.target_effect_id_;
+}
+
+gfx::Rect ClipExpander::MapRect(const gfx::Rect& rect,
+                                const PropertyTrees* property_trees) const {
+  switch (expander_type_) {
+    case ExpanderType::FILTER: {
+      const EffectNode* effect_node =
+          property_trees->effect_tree.Node(target_effect_id_);
+      gfx::Transform filter_draw_transform;
+      filter_draw_transform.Scale(effect_node->surface_contents_scale.x(),
+                                  effect_node->surface_contents_scale.y());
+      return effect_node->filters.MapRect(rect, filter_draw_transform.matrix());
+    }
+  }
+  NOTREACHED();
+  return gfx::Rect();
+}
+
+gfx::Rect ClipExpander::MapRectReverse(
+    const gfx::Rect& rect,
+    const PropertyTrees* property_trees) const {
+  switch (expander_type_) {
+    case ExpanderType::FILTER: {
+      const EffectNode* effect_node =
+          property_trees->effect_tree.Node(target_effect_id_);
+      gfx::Transform filter_draw_transform;
+      filter_draw_transform.Scale(effect_node->surface_contents_scale.x(),
+                                  effect_node->surface_contents_scale.y());
+      return effect_node->filters.MapRectReverse(
+          rect, filter_draw_transform.matrix());
+    }
+  }
+  NOTREACHED();
+  return gfx::Rect();
+}
+
+}  // namespace cc