Make Service own ServiceContext.

services/ui/demo/mus_demo.h

Index: services/ui/demo/mus_demo.h
diff --git a/services/ui/demo/mus_demo.h b/services/ui/demo/mus_demo.h
index 65d285a1ee5ca2eebc942e8133bc4cdb890b150b..8957cc4f54fa4eeaa69a26ed8bfe70836ec81fe5 100644
--- a/services/ui/demo/mus_demo.h
+++ b/services/ui/demo/mus_demo.h
@@ -35,9 +35,7 @@ class MusDemo : public shell::Service,
 
  private:
   // shell::Service:
-  void OnStart(shell::Connector* connector,
-               const shell::Identity& identity,
-               uint32_t id) override;
+  void OnStart(const shell::Identity& identity) override;
   bool OnConnect(shell::Connection* connection) override;
 
   // WindowTreeClientDelegate:
@@ -69,8 +67,6 @@ class MusDemo : public shell::Service,
   // Draws one frame, incrementing the rotation angle.
   void DrawFrame();
 
-  shell::Connector* connector_ = nullptr;
-
   Window* window_ = nullptr;
   WindowTreeClient* window_tree_client_ = nullptr;