Extract shell methods from ApplicationImpl into a base class, and pass this to Initialize() instead.

content/browser/renderer_host/render_widget_host_view_mus.cc

Index: content/browser/renderer_host/render_widget_host_view_mus.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_mus.cc b/content/browser/renderer_host/render_widget_host_view_mus.cc
index 3cfdacf4c85ae3075e6d0b7b08f53a00ffc144be..7f746427978c851f13e0561110adde382d007927 100644
--- a/content/browser/renderer_host/render_widget_host_view_mus.cc
+++ b/content/browser/renderer_host/render_widget_host_view_mus.cc
@@ -14,7 +14,7 @@
 #include "content/browser/renderer_host/render_widget_host_impl.h"
 #include "content/common/render_widget_window_tree_client_factory.mojom.h"
 #include "content/public/common/mojo_shell_connection.h"
-#include "mojo/shell/public/cpp/application_impl.h"
+#include "mojo/shell/public/cpp/shell.h"
 #include "ui/aura/client/screen_position_client.h"
 #include "ui/aura/window.h"
 #include "ui/base/hit_test.h"
@@ -40,7 +40,7 @@ RenderWidgetHostViewMus::RenderWidgetHostViewMus(mus::Window* parent_window,
   // and embed that client inside our mus window.
   std::string url = GetMojoApplicationInstanceURL(host_->GetProcess());
   mojom::RenderWidgetWindowTreeClientFactoryPtr factory;
-  MojoShellConnection::Get()->GetApplication()->ConnectToService(url, &factory);
+  MojoShellConnection::Get()->GetShell()->ConnectToService(url, &factory);
 
   mus::mojom::WindowTreeClientPtr window_tree_client;
   factory->CreateWindowTreeClientForRenderWidget(