Long press menu (shift+f6) to toggle spoken feedback.

chrome/browser/ui/ash/chrome_shell_delegate_chromeos.cc

Index: chrome/browser/ui/ash/chrome_shell_delegate_chromeos.cc
diff --git a/chrome/browser/ui/ash/chrome_shell_delegate_chromeos.cc b/chrome/browser/ui/ash/chrome_shell_delegate_chromeos.cc
index ab915283658153a6c9148f92d7f21f2695982456..87b36ede875c1de29061399e654becb9cdec68cf 100644
--- a/chrome/browser/ui/ash/chrome_shell_delegate_chromeos.cc
+++ b/chrome/browser/ui/ash/chrome_shell_delegate_chromeos.cc
@@ -4,6 +4,7 @@
 
 #include "chrome/browser/ui/ash/chrome_shell_delegate.h"
 
+#include "ash/accelerators/spoken_feedback_toggler.h"
 #include "ash/accessibility_delegate.h"
 #include "ash/magnifier/magnifier_key_scroller.h"
 #include "ash/media_delegate.h"
@@ -57,6 +58,7 @@ void InitAfterSessionStart() {
   // Enable magnifier accelerators as there may be no mouse cursor in
   // kiosk mode.

[xiyuan, 2014/02/14 01:50:21]

Update the comment?

[oshima, 2014/02/14 18:03:25]

Done.

   ash::MagnifierKeyScroller::SetEnabled(chrome::IsRunningInForcedAppMode());
+  ash::SpokenFeedbackToggler::SetEnabled(chrome::IsRunningInForcedAppMode());
 }
 
 class AccessibilityDelegateImpl : public ash::AccessibilityDelegate {