Add Browser Task Scheduler Flags to iOS

ios/chrome/app/strings/ios_strings.grd

 <?xml version="1.0" encoding="UTF-8"?>
 
 <!--
 This file contains definition of resources that will be translated for each
 locale.  The variables is_win, is_macosx, is_linux, is_ios and is_posix are
 available for making strings OS specific.  Other platform defines such as
 use_titlecase are declared in build/common.gypi.
 
 The strings in this file are specific to iOS, thus is_ios will be true and
 all other OS specific variables will be false.
@@ skipping 244 matching lines @@
       </message>
       <message name="IDS_IOS_ACCNAME_VOICE_SEARCH" desc="The accessibility label for the voice search button in the location bar [Length: unlimited]">
         Voice Search
       </message>
 
       <!-- The URL for Google Chrome privacy policy. -->
       <message name="IDS_IOS_PRIVACY_POLICY_URL" translateable="false">
         http://www.google.com/intl/[GRITLANGCODE]/chrome/browser/privacy/
       </message>
 
+      <!-- Browser Task Scheduler -->
+      <message name="IDS_FLAGS_BROWSER_TASK_SCHEDULER_NAME"

[rohitrao (ping after 24h), 2016/10/25 12:07:07]

Could you name these IDS_IOS_FLAGS_, for consistency with the other names in
this file?

[robliao, 2016/10/26 17:28:19]

Done.

+               desc="Name of about:flag option to control the availability of the browser task scheduler."
+               translateable="false">
+        Browser Task Scheduler
+      </message>
+      <message name="IDS_FLAGS_BROWSER_TASK_SCHEDULER_DESCRIPTION"
+               desc="Description of about:flag option to control the availability of the browser task scheduler."
+               translateable="false">
+        Enables the browser task scheduler to dispatch tasks instead of the existing worker pools. The browser task scheduler will only be used if variation parameters are available.
+      </message>
+
     </messages>
   </release>
 </grit>