Move ZoomObserver, ZoomController and ZoomEventManager to components/.

chrome/browser/ui/zoom/zoom_event_manager.h

-// Copyright 2014 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 CHROME_BROWSER_UI_ZOOM_ZOOM_EVENT_MANAGER_H_
-#define CHROME_BROWSER_UI_ZOOM_ZOOM_EVENT_MANAGER_H_
-
-#include "base/callback_list.h"
-#include "base/memory/weak_ptr.h"
-#include "base/supports_user_data.h"
-#include "content/public/browser/host_zoom_map.h"
-
-namespace content {
-class BrowserContext;
-}  // namespace content
-
-// This class serves as a target for event notifications from all ZoomController
-// objects. Classes that need to know about browser-specific zoom events (e.g.
-// manual-mode zoom) should subscribe here.
-class ZoomEventManager : public base::SupportsUserData::Data {
- public:
-  ZoomEventManager();
-  ~ZoomEventManager() override;
-
-  // Returns the ZoomEventManager for the specified BrowserContext. This
-  // function creates the ZoomEventManager if it hasn't been created already.
-  static ZoomEventManager* GetForBrowserContext(
-      content::BrowserContext* context);
-
-  // Called by ZoomControllers when changes are made to zoom levels in manual
-  // mode in order that browser listeners can be notified.
-  void OnZoomLevelChanged(const content::HostZoomMap::ZoomLevelChange& change);
-
-  // Add and remove zoom level changed callbacks.
-  scoped_ptr<content::HostZoomMap::Subscription> AddZoomLevelChangedCallback(
-      const content::HostZoomMap::ZoomLevelChangedCallback& callback);
-
-  // Get a weak ptr to be used by clients who may themselves be UserData for
-  // the context, since the order of destruction is undefined between the client
-  // and this class.
-  base::WeakPtr<ZoomEventManager> GetWeakPtr() {
-    return weak_ptr_factory_.GetWeakPtr();
-  }
-
- private:
-  base::CallbackList<void(const content::HostZoomMap::ZoomLevelChange&)>
-      zoom_level_changed_callbacks_;
-  base::WeakPtrFactory<ZoomEventManager> weak_ptr_factory_;
-
-  DISALLOW_COPY_AND_ASSIGN(ZoomEventManager);
-};
-
-#endif  // CHROME_BROWSER_UI_ZOOM_ZOOM_EVENT_MANAGER_H_