Split //blimp/client/core to relevant parts.

blimp/client/public/blimp_contents_observer.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_OBSERVER_H_
-#define BLIMP_CLIENT_PUBLIC_BLIMP_CONTENTS_OBSERVER_H_
-
-#include "base/macros.h"
-#include "url/gurl.h"
-
-namespace blimp {
-namespace client {
-
-// An observer API implemented by classes which are interested in various events
-// related to BlimpContents.
-class BlimpContentsObserver {
- public:
-  virtual ~BlimpContentsObserver() = default;
-
-  // Invoked when the URL of the BlimpContents is changes.
-  virtual void OnURLUpdated(const GURL& url) {}
-
- protected:
-  BlimpContentsObserver() {}
-
- private:
-  DISALLOW_COPY_AND_ASSIGN(BlimpContentsObserver);
-};
-
-}  // namespace client
-}  // namespace blimp
-
-#endif  // BLIMP_CLIENT_PUBLIC_BLIMP_CONTENTS_OBSERVER_H_