Create a field test for sync sign in promo strings.

chrome/app/generated_resources.grd

 <?xml version="1.0" encoding="UTF-8"?>
 
 <!--
 This file contains definitions of resources that will be translated for each
 locale.  The variables is_win, is_macosx, is_linux, and is_posix are available
 for making strings OS specific.  Other platform defines such as use_titlecase
 are declared in build/common.gypi.
 -->
 
 <grit base_dir="." latest_public_release="0" current_release="1"
@@ skipping 10801 matching lines @@
       <!-- Sync promo page chrome://syncpromo -->
       <message name="IDS_SYNC_PROMO_TAB_TITLE" desc="The title of the sync promo tab.">
         Sign in
       </message>
       <message name="IDS_SYNC_PROMO_TITLE" desc="The title at the top of the sync promo">
         Welcome to <ph name="PRODUCT_NAME">$1<ex>Google Chrome</ex></ph>
       </message>
       <message name="IDS_SYNC_PROMO_MESSAGE_TITLE" desc="The first part of the sync promo message.">
         Set up <ph name="SHORT_PRODUCT_NAME">$1<ex>Chrome</ex></ph> with your Google Account
       </message>
-      <message name="IDS_SYNC_PROMO_MESSAGE_BODY" desc="The body of the sync promo message. This is followed by a learn more link.">
+      <message name="IDS_SYNC_PROMO_MESSAGE_BODY_A" desc="The body of the sync promo message. This is experiment choice 0, and the control/default message.">
         Get your bookmarks, history, and settings on all your devices.
       </message>
+      <message name="IDS_SYNC_PROMO_MESSAGE_BODY_B" desc="The body of the sync promo message. Experiment choice 1.">
+        Back up your bookmarks, history, and settings online.
+      </message>
+      <message name="IDS_SYNC_PROMO_MESSAGE_BODY_C" desc="The body of the sync promo message. Experiment choice 2.">
+        Sync your personalized browser features between all your devices.
+      </message>
+      <message name="IDS_SYNC_PROMO_MESSAGE_BODY_D" desc="The body of the sync promo message. Experiment choice 3.">
+        Get your bookmarks, history, and settings on all your devices. Plus, you'll be automatically signed in to your favorite Google services.
+      </message>
       <if expr="pp_ifdef('use_titlecase')">
         <message name="IDS_SYNC_PROMO_SKIP_BUTTON" desc="In Title Case: The button at the bottom to let the user skip the sync promo.">
           No Thanks
         </message>
       </if>
       <if expr="not pp_ifdef('use_titlecase')">
         <message name="IDS_SYNC_PROMO_SKIP_BUTTON" desc="The button at the bottom to let the user skip the sync promo.">
           No thanks
         </message>
       </if>
@@ skipping 3861 matching lines @@
     </messages>
     <structures fallback_to_english="true">
       <!-- Make sure these stay in sync with the structures in generated_resources.grd. -->
       <structure name="IDD_CHROME_FRAME_FIND_DIALOG" file="cf_resources.rc" type="dialog" >
       </structure>
       <structure name="IDD_CHROME_FRAME_READY_PROMPT" file="cf_resources.rc" type="dialog" >
       </structure>
     </structures>
   </release>
 </grit>