Add BlimpClientContext and factory with real and dummy implementation

blimp/client/public/blimp_contents.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BLIMP_CLIENT_PUBLIC_BLIMP_CONTENTS_H_
 #define BLIMP_CLIENT_PUBLIC_BLIMP_CONTENTS_H_
 
 #include "base/macros.h"
+#include "base/supports_user_data.h"
 #include "url/gurl.h"
 
 namespace blimp {
 namespace client {
 
 class BlimpContentsObserver;
 class BlimpNavigationController;
 
 // BlimpContents is the core class in //blimp/client/core. It renders web pages
 // from an engine in a rectangular area.
 // It enables callers to control the blimp engine through the use of the
 // navigation controller.
-class BlimpContents {
+class BlimpContents : public base::SupportsUserData {
  public:
-  virtual ~BlimpContents() = default;
-
   // Retrives the navigation controller that controls all navigation related
   // to this BlimpContents.
   virtual BlimpNavigationController& GetNavigationController() = 0;
 
   // Enables adding and removing observers to this BlimpContents.
   virtual void AddObserver(BlimpContentsObserver* observer) = 0;
   virtual void RemoveObserver(BlimpContentsObserver* observer) = 0;
 
  protected:
   BlimpContents() {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(BlimpContents);
 };
 
 }  // namespace client
 }  // namespace blimp
 
 #endif  // BLIMP_CLIENT_PUBLIC_BLIMP_CONTENTS_H_