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..26f12c48bbe1af6d596ca09249c2204906cff893
--- /dev/null
+++ b/cc/trees/clip_expander.cc
@@ -0,0 +1,43 @@
+// Copyright 2017 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(int filter_effect_id)
+    : target_effect_id_(filter_effect_id) {}
+
+ClipExpander::ClipExpander(const ClipExpander& other) = default;
+
+bool ClipExpander::operator==(const ClipExpander& other) const {
+  return target_effect_id_ == other.target_effect_id_;
+}
+
+gfx::Rect ClipExpander::MapRect(const gfx::Rect& rect,
+                                const PropertyTrees* property_trees) const {
+  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());
+}
+
+gfx::Rect ClipExpander::MapRectReverse(
+    const gfx::Rect& rect,
+    const PropertyTrees* property_trees) const {
+  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());
+}
+
+}  // namespace cc