Handle both plural and singular tab switcher content descriptions.

chrome/android/java/res/layout/toolbar.xml

 <?xml version="1.0" encoding="utf-8"?>
 <!-- Copyright 2015 The Chromium Authors. All rights reserved.
      Use of this source code is governed by a BSD-style license that can be
      found in the LICENSE file. -->
 
 <!-- The toolbar containing the URL bar, back button, and NTP button.
 -->
 
 <org.chromium.chrome.browser.toolbar.ToolbarPhone
     xmlns:android="http://schemas.android.com/apk/res/android"
@@ skipping 38 matching lines @@
         android:layout_height="wrap_content"
         android:layout_gravity="top|end" >
 
         <Space
             android:layout_width="4dp"
             android:layout_height="match_parent" />
 
         <ImageButton android:id="@+id/tab_switcher_button"
             style="@style/ToolbarButton"
             android:layout_gravity="top"
-            android:contentDescription="@string/accessibility_toolbar_btn_tabswitcher_toggle" />
+            android:contentDescription="@string/accessibility_toolbar_btn_tabswitcher_toggle_default" />
 
         <FrameLayout
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:id="@+id/menu_button_wrapper" >
 
             <org.chromium.chrome.browser.widget.TintedImageButton
                 android:id="@+id/menu_button"
                 style="@style/ToolbarMenuButtonPhone"
                 android:src="@drawable/btn_menu"
@@ skipping 10 matching lines @@
     </LinearLayout>
 
     <org.chromium.chrome.browser.widget.ToolbarProgressBar
         android:id="@+id/progress"
         android:layout_width="match_parent"
         android:layout_height="@dimen/toolbar_progress_bar_height"
         chrome:progressBarColor="@color/progress_bar_foreground"
         chrome:backgroundColor="@color/progress_bar_background" />
 
 </org.chromium.chrome.browser.toolbar.ToolbarPhone>