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

ui/views/mus/surface_binding.h

Index: ui/views/mus/surface_binding.h
diff --git a/ui/views/mus/surface_binding.h b/ui/views/mus/surface_binding.h
index b0fdbc6558109609bb3cd0f3daba05c4dcb5a26f..0b468b574e49829793f21e6701da9e2ade1a0229 100644
--- a/ui/views/mus/surface_binding.h
+++ b/ui/views/mus/surface_binding.h
@@ -16,12 +16,8 @@ class OutputSurface;
 }
 
 namespace mojo {
-namespace shell {
-namespace mojom {
 class Shell;
 }
-}
-}
 
 namespace mus {
 class Window;
@@ -36,7 +32,7 @@ namespace views {
 // connection.
 class VIEWS_MUS_EXPORT SurfaceBinding {
  public:
-  SurfaceBinding(mojo::shell::mojom::Shell* shell,
+  SurfaceBinding(mojo::Shell* shell,
                  mus::Window* window,
                  mus::mojom::SurfaceType surface_type);
   ~SurfaceBinding();