Make reftests work for sky.

sky/viewer/document_view.cc

Index: sky/viewer/document_view.cc
diff --git a/sky/viewer/document_view.cc b/sky/viewer/document_view.cc
index 51eae14a4c3aa48952c152ec157ee0c27f8d7678..f7cb1833d3ca77753cd107526c35f7cb9a6fd570 100644
--- a/sky/viewer/document_view.cc
+++ b/sky/viewer/document_view.cc
@@ -73,15 +73,17 @@ static int s_next_debugger_id = 1;
 DocumentView::DocumentView(
     mojo::ServiceProviderPtr provider,
     mojo::URLResponsePtr response,
-    mojo::Shell* shell)
+    mojo::Shell* shell,
+    bool is_testing)
     : response_(response.Pass()),
       shell_(shell),
       web_view_(NULL),
       root_(NULL),
       view_manager_client_factory_(shell_, this),
       inspector_service_factory_(this),
+      weak_factory_(this),
       debugger_id_(s_next_debugger_id++),
-      weak_factory_(this) {
+      is_testing_(is_testing) {
   exported_services_.AddService(&view_manager_client_factory_);
   mojo::WeakBindToPipe(&exported_services_, provider.PassMessagePipe());
 }
@@ -131,10 +133,14 @@ void DocumentView::Load(mojo::URLResponsePtr response) {
 
 void DocumentView::initializeLayerTreeView() {
   layer_host_.reset(new LayerHost(this));
-  root_layer_ = make_scoped_refptr(new Layer(this));
+  root_layer_ = make_scoped_refptr(new Layer(this, is_testing_));
   layer_host_->SetRootLayer(root_layer_);
 }
 
+std::string DocumentView::GetPixelsForTesting() {
+  return layer_host_->GetPixelsForTesting();
+}
+
 mojo::Shell* DocumentView::GetShell() {
   return shell_;
 }