Implement media Cast button in Blink

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 439 matching lines @@
         exit full screen
       </message>
 
       <message name="IDS_AX_MEDIA_SHOW_CLOSED_CAPTIONS_BUTTON" desc="accessibility role description for show closed captions button">
         show closed captions
       </message>
 
       <message name="IDS_AX_MEDIA_HIDE_CLOSED_CAPTIONS_BUTTON" desc="accessibility role description for hide closed captions button">
         hide closed captions
       </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_AUDIO_ELEMENT_HELP" desc="Accessible help of audio controls">
         audio
       </message>
 
       <message name="IDS_AX_MEDIA_VIDEO_ELEMENT_HELP" desc="Accessible help of video">
         video
       </message>
 
       <message name="IDS_AX_MEDIA_MUTE_BUTTON_HELP" desc="accessibility help description for mute button">
@@ skipping 41 matching lines @@
       </message>
 
       <message name="IDS_AX_MEDIA_SHOW_CLOSED_CAPTIONS_BUTTON_HELP" desc="accessibility help description for show closed captions button">
         start displaying closed captions
       </message>
 
       <message name="IDS_AX_MEDIA_HIDE_CLOSED_CAPTIONS_BUTTON_HELP" desc="accessibility help description for hide closed captions button">
         stop displaying closed captions
       </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_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
       </message>
 
       <message name="IDS_AX_MONTH_FIELD_TEXT" desc="Accessible description of the month field in a date/time control">
         Month
@@ skipping 144 matching lines @@
         Please shorten this text to <ph name="MAX_CHARACTERS">$2<ex>100</ex></ph> characters or less (you are currently using <ph name="CURRENT_LENGTH">$1<ex>101</ex></ph> characters).
       </message>
 
       <message name="IDS_PLUGIN_INITIALIZATION_ERROR" desc="A message displayed when a plug-in failed to load">
         Couldn't load plug-in.
       </message>
 
     </messages>
   </release>
 </grit>