Introduce Property Trees

cc/trees/layer_tree_host_common.cc

Index: cc/trees/layer_tree_host_common.cc
diff --git a/cc/trees/layer_tree_host_common.cc b/cc/trees/layer_tree_host_common.cc
index 6863850c97b01c7e98fac52450e1609742ec8948..7fce94bbac40a56a598e9385791b8be468ec9f7d 100644
--- a/cc/trees/layer_tree_host_common.cc
+++ b/cc/trees/layer_tree_host_common.cc
@@ -14,7 +14,9 @@
 #include "cc/layers/layer_iterator.h"
 #include "cc/layers/render_surface.h"
 #include "cc/layers/render_surface_impl.h"
+#include "cc/trees/draw_property_utils.h"
 #include "cc/trees/layer_sorter.h"
+#include "cc/trees/layer_tree_host.h"
 #include "cc/trees/layer_tree_impl.h"
 #include "ui/gfx/geometry/rect_conversions.h"
 #include "ui/gfx/transform.h"
@@ -2400,6 +2402,14 @@ static void ProcessCalcDrawPropsInputs(
   data_for_recursion->subtree_is_visible_from_ancestor = true;
 }
 
+static bool ApproximatelyEqual(const gfx::Rect& r1, const gfx::Rect& r2) {
+  static const int tolerance = 1;
+  return std::abs(r1.x() - r2.x()) <= tolerance &&
+         std::abs(r1.y() - r2.y()) <= tolerance &&
+         std::abs(r1.width() - r2.width()) <= tolerance &&
+         std::abs(r1.height() - r2.height()) <= tolerance;
+}
+
 void LayerTreeHostCommon::CalculateDrawProperties(
     CalcDrawPropsMainInputs* inputs) {
   LayerList dummy_layer_list;
@@ -2424,6 +2434,41 @@ void LayerTreeHostCommon::CalculateDrawProperties(
   // A root layer render_surface should always exist after
   // CalculateDrawProperties.
   DCHECK(inputs->root_layer->render_surface());
+
+  // Now compare with the new approach.
+  //
+  // TODO(ajuma): Can we efficiently cache some of this rather than
+  // starting from scratch every frame?
+  //
+  // TODO(vollick): This needs to be cleaned up, moved, and enabled with a
+  // runtime flag.
+  TransformTree transform_tree;
+  ClipTree clip_tree;
+  ComputeVisibleRectsUsingPropertyTrees(inputs->root_layer,
+                                        inputs->page_scale_application_layer,
+                                        inputs->page_scale_factor,
+                                        inputs->device_scale_factor,
+                                        gfx::Rect(inputs->device_viewport_size),
+                                        inputs->device_transform,
+                                        &transform_tree,
+                                        &clip_tree);
+
+  bool failed = false;
+  LayerIterator<Layer> it, end;
+  for (it = LayerIterator<Layer>::Begin(inputs->render_surface_layer_list),
+      end = LayerIterator<Layer>::End(inputs->render_surface_layer_list);
+       it != end; ++it) {
+    Layer* current_layer = *it;
+    if (it.represents_itself()) {
+      if (!failed && current_layer->DrawsContent() &&
+          !ApproximatelyEqual(current_layer->visible_content_rect(),
+                              current_layer->debug_visible_rect())) {
+        failed = true;
+      }
+    }
+  }
+
+  CHECK(!failed);
 }
 
 void LayerTreeHostCommon::CalculateDrawProperties(