Expose caps lock state as an accessible alert

ash/common/system/chromeos/tray_caps_lock.cc

Index: ash/common/system/chromeos/tray_caps_lock.cc
diff --git a/ash/common/system/chromeos/tray_caps_lock.cc b/ash/common/system/chromeos/tray_caps_lock.cc
index 5fed32498e8f8ea41b88bf5982eb85ed010f6254..5ede08bf5952fd458663d5c45e6cce61cd6fd15b 100644
--- a/ash/common/system/chromeos/tray_caps_lock.cc
+++ b/ash/common/system/chromeos/tray_caps_lock.cc
@@ -4,6 +4,7 @@
 
 #include "ash/common/system/chromeos/tray_caps_lock.h"
 
+#include "ash/common/accessibility_delegate.h"
 #include "ash/common/material_design/material_design_controller.h"
 #include "ash/common/system/tray/actionable_view.h"
 #include "ash/common/system/tray/system_tray_delegate.h"
@@ -159,6 +160,10 @@ TrayCapsLock::~TrayCapsLock() {
 void TrayCapsLock::OnCapsLockChanged(bool enabled) {
   caps_lock_enabled_ = enabled;
 
+  // Send an a11y alert.
+  WmShell::Get()->accessibility_delegate()->TriggerAccessibilityAlert(
+      enabled ? A11Y_ALERT_CAPS_ON : A11Y_ALERT_CAPS_OFF);
+
   if (tray_view())
     tray_view()->SetVisible(caps_lock_enabled_);