Add a menu option for the right-hand Ctrl -> Meta mapping.

remoting/resources/remoting_strings.grd

 <?xml version="1.0" encoding="UTF-8"?>
 
 <grit base_dir="." current_release="1" enc_check="möl" latest_public_release="0" source_lang_id="en">
   <outputs>
     <output filename="remoting/base/string_resources.h" type="rc_header">
       <emit emit_type="prepend"/>
     </output>
 
     <output filename="remoting/resources/am.pak" lang="am" type="data_package"/>
     <output filename="remoting/resources/ar.pak" lang="ar" type="data_package"/>
@@ skipping 985 matching lines @@
       </message>
       <message desc="Label for the client-side menu button that sends a Ctrl-Alt-Del sequence to the host. Clicking this button behaves as if Ctrl, Alt and Del were pressed and then released at the host." name="IDS_SEND_CTRL_ALT_DEL" formatter_data="android_java">
         Send Ctrl-Alt-Del
       </message>
       <message desc="Tool-bar button used to access buttons for pressing and releasing keys or sequences of keys that might not otherwise be available. For example, Ctrl-Alt-Del, which if pressed at a client would take effect there, rather than being sent to the host as the user expected." name="IDS_SEND_KEYS">
         Send keys
       </message>
       <message desc="Label for the client-side menu button that sends a PrtScn key press to the host. The 'PrtScn' abbreviation (as typically printed on the keycap on English keyboards) is preferred over 'Print Screen', to make it clearer that this refers to the physical PrtScn key, and not the OS-specific keyboard shortcut for the screen capture functionality." name="IDS_SEND_PRINT_SCREEN">
         Send PrtScn
       </message>
+      <message desc="Label for the client-side menu button that toggles whether or not the right-hand Ctrl key is used to send the Windows/Command key." name="IDS_MAP_RIGHT_CTRL_TO_META">
+        Use right Ctrl for Win key (⌘ on Mac)
+      </message>
       <message desc="Menu option for enabling shrink-to-fit. When clicked, the remote desktop will be scaled down so that it fits in the browser window." name="IDS_SHRINK_TO_FIT">
         Shrink to fit
       </message>
       <message desc="Sign in button, visible if the user's authentication token is corrupt, in which case the user has to sign in (authenticate) to the app again." name="IDS_SIGN_IN_BUTTON">
         Sign in
       </message>
       <message desc="Sign out button, visible if the user has authenticated. Clicking this clears authentication credentials and returns the web-app to the initial 'unauthenticated' state." name="IDS_SIGN_OUT_BUTTON">
         Sign out
       </message>
       <message desc="Label for the 'stop sharing' button on the host-side. Clicking this button disconnects the client." name="IDS_STOP_SHARING_BUTTON">
@@ skipping 122 matching lines @@
       <message desc="Label for the button to decline sharing the computer in 'It2Me' mode." name="IDS_SHARE_CONFIRM_DIALOG_DECLINE" >
         Cancel
       </message>
       <message desc="Text shown in tooltip to inform the user that a setting is managed by domain policy." name="IDS_SETTING_MANAGED_BY_POLICY">
         This setting is managed by your domain policy.
       </message>
 
     </messages>
   </release>
 </grit>