Make reftests work for sky.

sky/viewer/content_handler_impl.h

Index: sky/viewer/content_handler_impl.h
diff --git a/sky/viewer/content_handler_impl.h b/sky/viewer/content_handler_impl.h
index 12360f35366122c2b6636b40a50154a4036cc287..dbd0838c736d72047086c1e8adf4c186ceff023e 100644
--- a/sky/viewer/content_handler_impl.h
+++ b/sky/viewer/content_handler_impl.h
@@ -14,7 +14,7 @@ class DocumentView;
 
 class ContentHandlerImpl : public mojo::InterfaceImpl<mojo::ContentHandler> {
  public:
-  ContentHandlerImpl();
+  ContentHandlerImpl(bool is_testing);
   ~ContentHandlerImpl() override;
 
  private:
@@ -22,6 +22,8 @@ class ContentHandlerImpl : public mojo::InterfaceImpl<mojo::ContentHandler> {
   void StartApplication(mojo::ShellPtr shell,
                         mojo::URLResponsePtr response) override;
 
+  bool is_testing_;
+
   DISALLOW_COPY_AND_ASSIGN(ContentHandlerImpl);
 };