Media Remoting: Add interstitial elements to media element shadow dom.

content/app/strings/content_strings.grd

 <?xml version="1.0" encoding="UTF-8"?>
 
 <!-- This file contains definitions of resources that will be translated for
 each locale. Specifically, these are UI strings that are used by content that
 need to be translated for each locale.-->
 
 <!-- Some of these strings and string descriptions were taken from
 WebKit/win/WebCoreLocalizedStrings.cpp so we include the original license
 below:
 
@@ skipping 581 matching lines @@
       </message>
 
       <message name="IDS_AX_MEDIA_CAST_OFF_BUTTON" desc="Accessibility role description for remote playback button">
         play on remote device
       </message>
 
       <message name="IDS_AX_MEDIA_CAST_ON_BUTTON" desc="Accessibility role description for remote playback control button">
         control remote playback
       </message>
 
+      <message name="IDS_AX_MEDIA_REMOTING_DISABLE_BUTTON" desc="Accessibility role description for media remoting disable button">
+        disable media remoting
+      </message>
+
       <message name="IDS_AX_MEDIA_DOWNLOAD_BUTTON" desc="Media controls download button.">
         download media
       </message>
 
       <message name="IDS_AX_MEDIA_OVERFLOW_BUTTON" desc="Media controls overflow button.">
         show more media controls
       </message>
 
       <message name="IDS_AX_MEDIA_AUDIO_ELEMENT_HELP" desc="Accessible help of audio controls">
         audio
@@ skipping 60 matching lines @@
       </message>
 
       <message name="IDS_AX_MEDIA_CAST_OFF_BUTTON_HELP" desc="Accessibility help description for remote playback button">
         play on remote device
       </message>
 
       <message name="IDS_AX_MEDIA_CAST_ON_BUTTON_HELP" desc="Accessibility help description for remote playback control button">
         control remote playback
       </message>
 
+      <message name="IDS_AX_MEDIA_REMOTING_DISABLE_BUTTON_HELP" desc="Accessibility help description for media remoting disable button">
+        disable media remoting
+      </message>
+
       <message name="IDS_AX_MEDIA_OVERFLOW_BUTTON_HELP" desc="Accessibility help description for overflow button.">
         more options
       </message>
 
       <message name="IDS_AX_MILLISECOND_FIELD_TEXT" desc="Accessible description of the millisecond field in a date/time control">
         Milliseconds
       </message>
 
       <message name="IDS_AX_MINUTE_FIELD_TEXT" desc="Accessible description of the minute field in a date/time control">
         Minutes
@@ skipping 185 matching lines @@
         Off
       </message>
 
       <message name="IDS_PLUGIN_INITIALIZATION_ERROR" desc="A message displayed when a plugin failed to load">
         Couldn't load plugin.
       </message>
 
     </messages>
   </release>
 </grit>