Fix Volume slider is captured in screenshot done in touchview mode

ash/common/system/tray/system_tray_notifier.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 ASH_COMMON_SYSTEM_TRAY_SYSTEM_TRAY_NOTIFIER_H_
 #define ASH_COMMON_SYSTEM_TRAY_SYSTEM_TRAY_NOTIFIER_H_
 
 #include <string>
 
 #include "ash/ash_export.h"
 #include "ash/common/accessibility_types.h"
 #include "ash/common/system/locale/locale_observer.h"
 #include "base/macros.h"
 #include "base/observer_list.h"
 
 #if defined(OS_CHROMEOS)
 #include "base/strings/string16.h"
 #include "base/time/time.h"
 #endif
 
 namespace ash {
 
 class AccessibilityObserver;
 class AudioObserver;
 class ClockObserver;
 class IMEObserver;
+class MaximizeModeScreenshotObserver;
 struct UpdateInfo;
 class UpdateObserver;
 class UserObserver;
 
 #if defined(OS_CHROMEOS)
 class BluetoothObserver;
 class EnterpriseDomainObserver;
 class LastWindowClosedObserver;
 class LogoutButtonObserver;
 class MediaCaptureObserver;
@@ skipping 53 matching lines @@
   void AddUpdateObserver(UpdateObserver* observer);
   void RemoveUpdateObserver(UpdateObserver* observer);
   void NotifyUpdateRecommended(const UpdateInfo& info);
 
   // User.
   void AddUserObserver(UserObserver* observer);
   void RemoveUserObserver(UserObserver* observer);
   void NotifyUserUpdate();
   void NotifyUserAddedToSession();
 
+  // Maximize mode screenshot.
+  void AddMaxModeScreenshotObserver(MaximizeModeScreenshotObserver* observer);

[Daniel Erat, 2016/07/27 23:51:31]

s/MaxMode/MaximizeMode/ here and on the next line; "MaxMode" doesn't look like
it's currently used anywhere in the code

[Qiang(Joe) Xu, 2016/07/28 03:27:18]

Done.

+  void RemoveMaxModeScreenshotObserver(
+      MaximizeModeScreenshotObserver* observer);
+  void NotifyWillTakeScreenshot(int volume_percent);
+  void NotifyDidTakeScreenshot();

[Daniel Erat, 2016/07/27 23:51:31]

maybe rename these to:

  NotifyWillTakeScreenshotInMaximizeMode
  NotifyDidTakeScreenshotInMaximizeMode

? the current names don't accurately reflect when they should be called. the
observer would need to be updated too.

actually, i'm wondering if the names should also explain that these are only
called for the volume-down+power accelerator in particular.

but it feels like this is so special-purpose that it's hard to justify an
observer interface. can PowerButtonController call directly into TrayAudio to
notify it about things, or is that a layering violation?

what about if TrayAudio had a SuppressNotification() method that PBC could call,
and then PBC handled saving the original volume and restoring it later all on
its own? that seems like it greatly cuts down the complexity of this change.

[Qiang(Joe) Xu, 2016/07/28 00:15:39]

Hi, to get a better understanding, what is SuppressNotification this paragraph
meaning? I cannot see a code example in code base. Thanks!

[Daniel Erat, 2016/07/28 00:25:56]

i meant that PBC could call a new TrayAudio method with a signature like:

  void SuppressNotification(bool suppress);

(or maybe HideNotification is clearer) when it wants to hide or unhide
notifications.

[Qiang(Joe) Xu, 2016/07/28 03:27:18]

I still keep MaximizeModeScreenshotObserver in SystemTrayNotifier for these
reasons.
1. I cannot figure out a way to call methods of TrayAudio from PBC.
2. |hide_popup_| needs to be set in TrayAudio and modifies
OnOutputNodeVolumeChanged method, which makes I believe it still needs the
observer.
3. I tried move the observer as a nested class in PBC, however
ash::Shell::GetInstance()->power_button_controller()->AddObserver in TrayAudio
breaks the DEPS rule. "ash/common" cannot includes "ash/".

For 1. SystemTray doesn't expose TrayAudio reference. Could I expose that?
https://cs.chromium.org/chromium/src/ash/common/system/tray/system_tray.h?q=s...
It only provides the accessors for testing purpose.

+
 #if defined(OS_CHROMEOS)
   // Bluetooth.
   void AddBluetoothObserver(BluetoothObserver* observer);
   void RemoveBluetoothObserver(BluetoothObserver* observer);
   void NotifyRefreshBluetooth();
   void NotifyBluetoothDiscoveringChanged();
 
   // Enterprise domain.
   void AddEnterpriseDomainObserver(EnterpriseDomainObserver* observer);
   void RemoveEnterpriseDomainObserver(EnterpriseDomainObserver* observer);
@@ skipping 57 matching lines @@
   void RemoveVirtualKeyboardObserver(VirtualKeyboardObserver* observer);
   void NotifyVirtualKeyboardSuppressionChanged(bool suppressed);
 #endif
 
  private:
   base::ObserverList<AccessibilityObserver> accessibility_observers_;
   base::ObserverList<AudioObserver> audio_observers_;
   base::ObserverList<ClockObserver> clock_observers_;
   base::ObserverList<IMEObserver> ime_observers_;
   base::ObserverList<LocaleObserver> locale_observers_;
+  base::ObserverList<MaximizeModeScreenshotObserver>
+      maximize_mode_screenshot_observers_;
   base::ObserverList<UpdateObserver> update_observers_;
   base::ObserverList<UserObserver> user_observers_;
 
 #if defined(OS_CHROMEOS)
   base::ObserverList<BluetoothObserver> bluetooth_observers_;
   base::ObserverList<EnterpriseDomainObserver> enterprise_domain_observers_;
   base::ObserverList<LastWindowClosedObserver> last_window_closed_observers_;
   base::ObserverList<LogoutButtonObserver> logout_button_observers_;
   base::ObserverList<MediaCaptureObserver> media_capture_observers_;
   base::ObserverList<NetworkObserver> network_observers_;
   base::ObserverList<NetworkPortalDetectorObserver>
       network_portal_detector_observers_;
   base::ObserverList<ScreenCaptureObserver> screen_capture_observers_;
   base::ObserverList<ScreenShareObserver> screen_share_observers_;
   base::ObserverList<SessionLengthLimitObserver>
       session_length_limit_observers_;
   base::ObserverList<TracingObserver> tracing_observers_;
   base::ObserverList<VirtualKeyboardObserver> virtual_keyboard_observers_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(SystemTrayNotifier);
 };
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_SYSTEM_TRAY_SYSTEM_TRAY_NOTIFIER_H_