MD Settings: Bluetooth: Add a11y label for toggle button

chrome/app/settings_strings.grdp

 <?xml version="1.0" encoding="utf-8"?>
 <!-- Settings-specific strings (included from generated_resources.grd). -->
 <grit-part>
   <!-- About Page -->
   <message name="IDS_SETTINGS_ABOUT_PAGE_BROWSER_VERSION" desc="The text label describing the version of the browser, example: Version 57.0.2937.0 (Developer Build) unknown (64-bit)">
     Version <ph name="PRODUCT_VERSION">$1<ex>15.0.865.0</ex></ph> (<ph name="PRODUCT_CHANNEL">$2<ex>Developer Build</ex></ph>) <ph name="PRODUCT_MODIFIER">$3</ph> <ph name="PRODUCT_VERSION_BITS">$4</ph>
   </message>
   <if expr="chromeos">
     <message name="IDS_SETTINGS_ABOUT_PAGE_DETAILED_BUILD_INFO" desc="Label describing the section that shows detailed information about the current Chrome build.">
       Detailed build information
@@ skipping 475 matching lines @@
     </message>
     <message name="IDS_SETTINGS_BLUETOOTH_NO_DEVICES_FOUND" desc="Message displayed when no Bluetooth devices are found after a scan.">
       No Bluetooth devices found.
     </message>
     <message name="IDS_SETTINGS_BLUETOOTH_ENABLED" desc="Label for Bluetooth section when enabled.">
       Enabled
     </message>
     <message name="IDS_SETTINGS_BLUETOOTH_DISABLED" desc="Label for Bluetooth section when disabled.">
       Disabled
     </message>
+    <message name="IDS_SETTINGS_BLUETOOTH_TOGGLE_ACCESSIBILITY_LABEL" desc="Accessibility only label for Bluetooth enable/disable toggle .">
+      Bluetooth enable
+    </message>
     <message name="IDS_SETTINGS_BLUETOOTH_EXPAND_ACCESSIBILITY_LABEL" desc="Label for the button that toggles showing available Bluetooth devices. Only visible by screen reader software.">
       Show available Bluetooth devices
     </message>
     <message name="IDS_SETTINGS_BLUETOOTH_REMOVE" desc="Label for removing (unpairing) a paired Bluetooth device">
       Remove from list
     </message>
     <message name="IDS_SETTINGS_BLUETOOTH_REQUEST_PINCODE" desc="Bluetooth pairing message typically displayed when the external Bluetooth 2.0 and older device has no display or means of input.">
       Please enter the PIN for "<ph name="DEVICE_NAME">$1<ex>Nexus S</ex></ph>":
     </message>
     <message name="IDS_SETTINGS_BLUETOOTH_DISPLAY_PINCODE" desc="Bluetooth pairing message typically displayed when pairing a Bluetooth 2.0 and older wireless keyboard.">
@@ skipping 2347 matching lines @@
       System
     </message>
     <message name="IDS_SETTINGS_SYSTEM_HARDWARE_ACCELERATION_LABEL" desc="Label for the checkbox that forces Chrome to render via hardware acceleration (GPU) when available.">
       Use hardware acceleration when available
     </message>
     <message name="IDS_SETTINGS_SYSTEM_PROXY_SETTINGS_BUTTON" desc="Text for the button that changes a user's network proxy settings.">
       Change proxy settings
     </message>
   </if>
 </grit-part>