arc: Implement scrollable OptIn window content.

chrome/browser/chromeos/arc/arc_support_host.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 CHROME_BROWSER_CHROMEOS_ARC_ARC_SUPPORT_HOST_H_
 #define CHROME_BROWSER_CHROMEOS_ARC_ARC_SUPPORT_HOST_H_
 
 #include "base/macros.h"
 #include "chrome/browser/chromeos/arc/arc_auth_service.h"
 #include "components/prefs/pref_change_registrar.h"
 #include "extensions/browser/api/messaging/native_message_host.h"
+#include "ui/display/display_observer.h"
 
 // Supports communication with Arc support dialog.
 class ArcSupportHost : public extensions::NativeMessageHost,
-                       public arc::ArcAuthService::Observer {
+                       public arc::ArcAuthService::Observer,
+                       public display::DisplayObserver {
  public:
   static const char kHostName[];
   static const char kHostAppId[];
   static const char kStorageId[];
   static const char* const kHostOrigin[];
 
   static std::unique_ptr<NativeMessageHost> Create();
 
   ~ArcSupportHost() override;
 
   // Overrides NativeMessageHost:
   void Start(Client* client) override;
   void OnMessage(const std::string& request_string) override;
   scoped_refptr<base::SingleThreadTaskRunner> task_runner() const override;
 
   // Overrides arc::ArcAuthService::Observer:
   void OnOptInUIClose() override;
   void OnOptInUIShowPage(arc::ArcAuthService::UIPage page,
                          const base::string16& status) override;
 
+  // display::DisplayObserver:
+  void OnDisplayAdded(const display::Display& new_display) override;
+  void OnDisplayRemoved(const display::Display& old_display) override;
+  void OnDisplayMetricsChanged(const display::Display& display,
+                               uint32_t changed_metrics) override;
+
  private:
   ArcSupportHost();
 
   void OnMetricsPreferenceChanged();
   void Initialize();
   void SendMetricsMode();
   void EnableMetrics(bool is_enabled);
   void EnableBackupRestore(bool is_enabled);
 
   // Unowned pointer.
   Client* client_ = nullptr;
 
   // Used to track metrics preference.
   PrefChangeRegistrar pref_change_registrar_;
 
   DISALLOW_COPY_AND_ASSIGN(ArcSupportHost);
 };
 
 #endif  // CHROME_BROWSER_CHROMEOS_ARC_ARC_SUPPORT_HOST_H_