Add --enable-panels flag to about:flags.

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 4358 matching lines @@
       </message>
       <message name="IDS_FLAGS_PRERENDER_FROM_OMNIBOX_DESCRIPTION" desc="Description for the flag to prerender from the omnibox">
         Prerender suggestions given in the omnibox.
       </message>
       <message name="IDS_FLAGS_ENABLE_ADDITIONAL_AUTOFILL_FEEDBACK_NAME" desc="Title for the flag to enable prompts for Autofill feedback">
         Send additional Autofill feedback
       </message>
       <message name="IDS_FLAGS_ENABLE_ADDITIONAL_AUTOFILL_FEEDBACK_DESCRIPTION" desc="Description for the flag to enable prompts for Autofill feedback">
         Help improve Autofill.  With this enabled, Chrome will occasionally prompt you to send additional feedback to the Autofill team.
       </message>
+      <message name="IDS_FLAGS_ENABLE_PANELS_NAME" desc="Name of the 'Enable Pane
+ls' lab.">
+        Panels
+      </message>
+      <message name="IDS_FLAGS_ENABLE_PANELS_DESCRIPTION" desc="Description for the flag to enable Panel windows.">
+        Enable experimental extensions to open Panel windows outside of the browser frame.
+      </message>
 
       <!-- Crashes -->
       <message name="IDS_CRASHES_TITLE" desc="Title for the chrome://crashes page.">
         Crashes
       </message>
       <message name="IDS_CRASHES_CRASH_COUNT_BANNER_FORMAT" desc="Format for crash count banner on chrome://crashes">
         Crashes (<ph name="CRASH_COUNT">$1<ex>3</ex></ph>)
       </message>
       <message name="IDS_CRASHES_CRASH_HEADER_FORMAT" desc="Format for crash entry headings on chrome://crashes">
         Crash ID <ph name="CRASH_ID">$1<ex>8fa95dbb6f2ec862</ex></ph>
@@ skipping 8521 matching lines @@
     </includes>
     <structures fallback_to_english="true">
       <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>