cros: Suspend media sessions with display off trigger by tablet power button

ash/system/power/tablet_power_button_controller.cc

Index: ash/system/power/tablet_power_button_controller.cc
diff --git a/ash/system/power/tablet_power_button_controller.cc b/ash/system/power/tablet_power_button_controller.cc
index 7d2fcc9c4b4e449120462abd010cf47885aab433..71483efa14d082cba0414bd22e67da98e45c55ab 100644
--- a/ash/system/power/tablet_power_button_controller.cc
+++ b/ash/system/power/tablet_power_button_controller.cc
@@ -222,6 +222,10 @@ void TabletPowerButtonController::SetDisplayForcedOff(bool forced_off) {
   backlights_forced_off_ = forced_off;
   UpdateTouchscreenStatus();
 
+  ShellDelegate* delegate = Shell::Get()->shell_delegate();
+  backlights_forced_off_ ? delegate->SuspendMediaSessions()
+                         : delegate->ResumeMediaSessions();

[Daniel Erat, 2017/05/17 01:22:25]

please update unit tests to check that this happens as expected.

[Qiang(Joe) Xu, 2017/05/22 22:58:47]

Done.

+
   // Send an a11y alert.
   Shell::Get()->accessibility_delegate()->TriggerAccessibilityAlert(
       forced_off ? A11Y_ALERT_SCREEN_OFF : A11Y_ALERT_SCREEN_ON);