Move visual rect unioning between paired items to cc::DisplayItemList.

ui/compositor/transform_recorder.cc

Index: ui/compositor/transform_recorder.cc
diff --git a/ui/compositor/transform_recorder.cc b/ui/compositor/transform_recorder.cc
index 5867a54b57ba54d38eeb6e9cec6effd94ad8f507..cdacadb9810d8605ac5e10499845723e9572dd78 100644
--- a/ui/compositor/transform_recorder.cc
+++ b/ui/compositor/transform_recorder.cc
@@ -15,16 +15,13 @@ TransformRecorder::TransformRecorder(const PaintContext& context)
 
 TransformRecorder::~TransformRecorder() {
   if (transformed_)
-    context_.list_->CreateAndAppendItem<cc::EndTransformDisplayItem>(
-        bounds_in_layer_);
+    context_.list_->CreateAndAppendPairedEndItem<cc::EndTransformDisplayItem>();
 }
 
-void TransformRecorder::Transform(const gfx::Transform& transform,
-                                  const gfx::Size& size_in_context) {
+void TransformRecorder::Transform(const gfx::Transform& transform) {
   DCHECK(!transformed_);
-  bounds_in_layer_ = context_.ToLayerSpaceBounds(size_in_context);
-  context_.list_->CreateAndAppendItem<cc::TransformDisplayItem>(
-      bounds_in_layer_, transform);
+  context_.list_->CreateAndAppendPairedBeginItem<cc::TransformDisplayItem>(
+      transform);
   transformed_ = true;
 }