Fix cc scrollbar layer issues with initialization, and use element ids throughout.

third_party/WebKit/Source/core/frame/VisualViewport.cpp

Index: third_party/WebKit/Source/core/frame/VisualViewport.cpp
diff --git a/third_party/WebKit/Source/core/frame/VisualViewport.cpp b/third_party/WebKit/Source/core/frame/VisualViewport.cpp
index df88ee803bfa54461706c43cd488b9ee9ce6ef08..a3263009d1bc4b1f88afc4ae8d63a8f2a0f56a3f 100644
--- a/third_party/WebKit/Source/core/frame/VisualViewport.cpp
+++ b/third_party/WebKit/Source/core/frame/VisualViewport.cpp
@@ -363,8 +363,9 @@ void VisualViewport::CreateLayerTree() {
   inner_viewport_scroll_layer_->PlatformLayer()->SetUserScrollable(true, true);
   if (MainFrame()) {
     if (Document* document = MainFrame()->GetDocument()) {
-      inner_viewport_scroll_layer_->SetElementId(CreateCompositorElementId(
-          DOMNodeIds::IdForNode(document), CompositorSubElementId::kViewport));
+      inner_viewport_scroll_layer_->SetElementId(
+          CreateCompositorElementId(DOMNodeIds::IdForNode(document),
+                                    CompositorElementIdNamespace::kViewport));
     }
   }