a11y: Add the number of unread notifications to ChromeVox.

Bug: 763181
Change-Id: I869ee1e72bddad2bf6b5aaf11c5480ae21a28da3
Reviewed-on: https://chromium-review.googlesource.com/701928Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Commit-Queue: min c <minch@chromium.org>
Cr-Commit-Position: refs/heads/master@{#506782}

ash/system/web_notification/web_notification_tray.cc

@@ -424,7 +424,10 @@ void WebNotificationTray::AnchorUpdated() {
 }
 
 base::string16 WebNotificationTray::GetAccessibleNameForTray() {
-  return l10n_util::GetStringUTF16(IDS_MESSAGE_CENTER_ACCESSIBLE_NAME);
+  return l10n_util::GetStringFUTF16Int(
+      IDS_MESSAGE_CENTER_ACCESSIBLE_NAME,
+      static_cast<int>(
+          message_center_tray_->message_center()->NotificationCount()));
 }
 
 void WebNotificationTray::HideBubbleWithView(

ui/strings/ui_strings.grd

@@ -608,7 +608,7 @@ need to be translated for each locale.-->
 
       <!-- Message center -->
       <message name="IDS_MESSAGE_CENTER_ACCESSIBLE_NAME" desc="The accessible name for the Notification Center window.">
-        Notification Center
+        Notification Center, <ph name="unread_notification_count">$1<ex>5</ex></ph> unread notifications
       </message>
       <message name="IDS_MESSAGE_CENTER_NOTIFICATION_ACCESSIBLE_NAME" desc="The accessible name for a single notification.">
         Notification