Add a Learn More link to the Physical Web opt-in activity

chrome/android/java/strings/android_chrome_strings.grd

 <?xml version="1.0" encoding="UTF-8"?>
 
 <!-- android_chrome_strings.grd contains strings for Chrome for Android.
 
 FAQ:
   - How do I add, change, or remove a string?
       Just update this file.
   - Translations will happen automatically??
       Yes, indeed. Just add your string before the branch point and
       make the description good.
@@ skipping 2271 matching lines @@
 
 You must have Bluetooth and Location turned on in order to use the Physical Web.
       </message>
       <message name="IDS_PHYSICAL_WEB_OPTIN_TITLE" desc="The title for a dialog inviting the user to opt-in to the Physical Web.">
         Chrome + Physical Web
       </message>
       <message name="IDS_PHYSICAL_WEB_OPTIN_DESCRIPTION" desc="Description of the Physical Web displayed in the opt-in dialog">
         Devices nearby you are broadcasting web pages over Bluetooth. Chrome will scan for pages and display them when you wake up your device. These pages will go through a Google service to improve the quality of page results.
 
 You can control the Physical Web in Chrome Settings.
+
+<ph name="BEGIN_LINK">&lt;learnmore&gt;</ph>Learn more<ph name="END_LINK">&lt;/learnmore&gt;</ph>
       </message>
       <message name="IDS_PHYSICAL_WEB_LIST_URLS_ACTIVITY_TITLE" desc="The title for a dialog that shows a list of URLs broadcasted from nearby devices.">
         The Physical Web
       </message>
       <message name="IDS_PHYSICAL_WEB_NOTIFICATION_TITLE" desc="The message displayed in a notification when there are nearby URLs.">
         Physical Web pages nearby
       </message>
       <message name="IDS_PHYSICAL_WEB_OPTIN_NOTIFICATION_TITLE" desc="The first line in a notification message informing the user there are nearby devices broadcasting URLs and Chrome can be used to browse the list of URLs.">
         Web pages are nearby
       </message>
@@ skipping 85 matching lines @@
       <!-- Migration strings -->
       <message name="IDS_TAB_SWITCHER_CALLOUT_HEADER" desc="Header for the Tab Switcher callout.">
         Quickly switch tabs
       </message>
       <message name="IDS_TAB_SWITCHER_CALLOUT_BODY" desc="Indicates that clicking the tab switcher button gives you quick access to your tabs.">
         Tap this button for quick access to your tabs.
       </message>
     </messages>
   </release>
 </grit>