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

ui/compositor/compositing_recorder.cc

Index: ui/compositor/compositing_recorder.cc
diff --git a/ui/compositor/compositing_recorder.cc b/ui/compositor/compositing_recorder.cc
index fd255c731efc546acb1eebc725e167eed5512dda..1c488e03a893d67cb8d1ce39da8b2ca63e2de3b2 100644
--- a/ui/compositor/compositing_recorder.cc
+++ b/ui/compositor/compositing_recorder.cc
@@ -12,27 +12,23 @@
 namespace ui {
 
 CompositingRecorder::CompositingRecorder(const PaintContext& context,
-                                         const gfx::Size& size_in_context,
                                          uint8_t alpha,
                                          bool lcd_text_requires_opaque_layer)
     : context_(context),
-      bounds_in_layer_(context.ToLayerSpaceBounds(size_in_context)),
       saved_(alpha < 255) {
   if (!saved_)
     return;
 
-  context_.list_->CreateAndAppendItem<cc::CompositingDisplayItem>(
-      bounds_in_layer_, alpha, SkXfermode::kSrcOver_Mode,
-      nullptr /* no bounds */, nullptr /* no color filter */,
-      lcd_text_requires_opaque_layer);
+  context_.list_->CreateAndAppendPairedBeginItem<cc::CompositingDisplayItem>(
+      alpha, SkXfermode::kSrcOver_Mode, nullptr /* no bounds */,
+      nullptr /* no color filter */, lcd_text_requires_opaque_layer);
 }
 
 CompositingRecorder::~CompositingRecorder() {
   if (!saved_)
     return;
 
-  context_.list_->CreateAndAppendItem<cc::EndCompositingDisplayItem>(
-      bounds_in_layer_);
+  context_.list_->CreateAndAppendPairedEndItem<cc::EndCompositingDisplayItem>();
 }
 
 }  // namespace ui