Enable default media session when ChromeVox is toggled.

chrome/browser/chromeos/accessibility/accessibility_manager.cc

Index: chrome/browser/chromeos/accessibility/accessibility_manager.cc
diff --git a/chrome/browser/chromeos/accessibility/accessibility_manager.cc b/chrome/browser/chromeos/accessibility/accessibility_manager.cc
index 744d724485a505756031c6051a4ed8cf0d0698d8..91fb771a6c90629cae0257542d455eb6dc54c219 100644
--- a/chrome/browser/chromeos/accessibility/accessibility_manager.cc
+++ b/chrome/browser/chromeos/accessibility/accessibility_manager.cc
@@ -76,6 +76,7 @@
 #include "extensions/common/host_id.h"
 #include "mash/public/interfaces/launchable.mojom.h"
 #include "media/audio/sounds/sounds_manager.h"
+#include "media/base/media_switches.h"
 #include "services/service_manager/public/cpp/connector.h"
 #include "ui/base/ime/chromeos/input_method_manager.h"
 #include "ui/base/resource/resource_bundle.h"
@@ -1310,6 +1311,12 @@ void AccessibilityManager::PostLoadChromeVox() {
     chromevox_panel_widget_observer_.reset(
         new ChromeVoxPanelWidgetObserver(chromevox_panel_->GetWidget(), this));
   }
+
+  if (!base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kEnableDefaultMediaSession)) {
+    base::CommandLine::ForCurrentProcess()->AppendSwitch(
+        switches::kEnableDefaultMediaSession);
+  }
 }
 
 void AccessibilityManager::PostUnloadChromeVox() {