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

chrome/browser/ui/ash/chrome_shell_delegate.cc

Index: chrome/browser/ui/ash/chrome_shell_delegate.cc
diff --git a/chrome/browser/ui/ash/chrome_shell_delegate.cc b/chrome/browser/ui/ash/chrome_shell_delegate.cc
index b550ad2e967d17fd79e488c9f81b614caf89f402..defacbb8a2a4cd87c299ad68d7d3897c44633b4b 100644
--- a/chrome/browser/ui/ash/chrome_shell_delegate.cc
+++ b/chrome/browser/ui/ash/chrome_shell_delegate.cc
@@ -60,6 +60,7 @@
 #include "chrome/browser/ui/browser_tabstrip.h"
 #include "chrome/browser/ui/browser_window.h"
 #include "chrome/browser/ui/scoped_tabbed_browser_displayer.h"
+#include "chrome/browser/ui/tab_contents/tab_contents_iterator.h"
 #include "chrome/common/pref_names.h"
 #include "chrome/grit/chromium_strings.h"
 #include "chrome/grit/generated_resources.h"
@@ -68,8 +69,10 @@
 #include "components/prefs/pref_service.h"
 #include "components/user_manager/user.h"
 #include "components/user_manager/user_manager.h"
+#include "content/public/browser/media_session.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/common/service_manager_connection.h"
+#include "media/base/media_switches.h"
 #include "ui/aura/window.h"
 #include "ui/base/ime/chromeos/input_method_manager.h"
 #include "ui/base/l10n/l10n_util.h"
@@ -463,6 +466,11 @@ void ChromeShellDelegate::PreInit() {
   // in Shell::Init.
   display_configuration_observer_.reset(
       new chromeos::DisplayConfigurationObserver());
+
+  // Append switch for SuspendMediaSessions() that will suspend media players
+  // without turning on audio focus.
+  base::CommandLine::ForCurrentProcess()->AppendSwitch(
+      ::switches::kEnableInternalMediaSession);

[Daniel Erat, 2017/05/22 23:38:34]

src/content/browser/media/session/media_session_controllers_manager.cc currently
contains the following:

bool IsMediaSessionEnabled() {
#if defined(OS_ANDROID)
  return true;
#else
  base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
  return command_line->HasSwitch(switches::kEnableInternalMediaSession) ||
         command_line->HasSwitch(switches::kEnableAudioFocus);
#endif
}

i think it'd be cleaner to change the condition to also check
defined(OS_CHROMEOS), probably along with a comment explaining why this is
needed on chrome os.

that's assuming that the media session owners agree, though. :-)

[Qiang(Joe) Xu, 2017/05/23 17:54:46]

Done. mlamouri@, do you agree on this?

 }
 
 void ChromeShellDelegate::PreShutdown() {
@@ -590,6 +598,13 @@ void ChromeShellDelegate::ToggleTouchpad() {
   chromeos::system::InputDeviceSettings::Get()->ToggleTouchpad();
 }
 
+void ChromeShellDelegate::SuspendMediaSessions() {
+  for (TabContentsIterator it; !it.done(); it.Next()) {
+    content::MediaSession::Get(*it)->Suspend(
+        content::MediaSession::SuspendType::SYSTEM);
+  }
+}
+
 keyboard::KeyboardUI* ChromeShellDelegate::CreateKeyboardUI() {
   return new ChromeKeyboardUI(ProfileManager::GetActiveUserProfile());
 }