New post-sideload UI:

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 4601 matching lines @@
       <message name="IDS_EXTENSION_UNINSTALL_PROMPT_TITLE" desc="Titlebar of the extension or app uninstallation prompt window">
         Confirm Removal
       </message>
       <message name="IDS_EXTENSION_RE_ENABLE_PROMPT_TITLE" desc="Titlebar of the extension or app prompt window when re-enabling an extension that requires additional permissions">
         Confirm Re-enable
       </message>
       <message name="IDS_EXTENSION_PERMISSIONS_PROMPT_TITLE" desc="Titlebar of the extension or app permissions prompt window">
         Confirm Permissions
       </message>
       <message name="IDS_EXTENSION_INSTALL_PROMPT_HEADING" desc="First bold line in the content area of the extension or app installation prompt. Asks the user if they want to install a particular extension or app.">
         Add "<ph name="EXTENSION_NAME">$1<ex>Gmail Checker</ex></ph>"?

[Jeffrey Yasskin, 2012/10/13 21:17:35]

It's interesting that the extension's name appears in the opposite one of title
vs. heading for normal vs external installs.

[Matt Perry, 2012/10/15 19:13:38]

Agreed. I'm just copying the spec, which I've now shared with you.

       </message>
       <message name="IDS_EXTENSION_BUNDLE_INSTALL_PROMPT_HEADING_EXTENSIONS" desc="First bold line in the content area of the extension bundle installation prompt. Asks the user if they want to install the set of extensions.">
         Install these extensions?
       </message>
       <message name="IDS_EXTENSION_BUNDLE_INSTALL_PROMPT_HEADING_APPS" desc="First bold line in the content area of the app bundle installation prompt. Asks the user if they want to install the set of apps.">
         Install these apps?
       </message>
       <message name="IDS_EXTENSION_BUNDLE_INSTALL_PROMPT_HEADING_EXTENSION_APPS" desc="First bold line in the content area of the extension and app bundle installation prompt. Asks the user if they want to install the set of apps and extensions.">
         Install these apps and extensions?
       </message>
@@ skipping 664 matching lines @@
 
       <!-- chrome://extension-info bubble -->
       <message name="IDS_EXTENSION_SCRIPT_POPUP_IS_RUNNING" desc="The label in the extension info bubble that indicates the extension is running scripts on this page">
         <ph name="EXTENSION_NAME">$1<ex>AdBlock</ex></ph> is running on this page.
       </message>
       <message name="IDS_EXTENSION_SCRIPT_POPUP_LAST_UPDATED" desc="The label in the extension info bubble indicating the last time an extension was updated.">
         Last updated:
       </message>
 
       <!-- Global error messages for extensions -->
-      <message name="IDS_EXTENSION_WARNINGS_WRENCH_MENU_ITEM" desc="The wrench menu item indicating that extensions caused problems">
+      <message name="IDS_EXTENSION_WARNINGS_WRENCH_MENU_ITEM" desc="The wrench menu item indicating that extensions caused problems.">
         Extension error
       </message>
       <message name="IDS_EXTENSION_WARNINGS_TITLE" desc="The title of a section in chrome://extensions which contains the warning(s) that relates to one particular extension">
         Warning:
       </message>
       <message name="IDS_EXTENSION_WARNINGS_NETWORK_DELAY" desc="Warning message indicating that an extension caused excessive network delays for web requests">
         This extension is slowing down <ph name="PRODUCT_NAME">$1<ex>Google Chrome</ex></ph>. You should disable it to restore <ph name="PRODUCT_NAME">$1<ex>Google Chrome</ex></ph>'s performance.
       </message>
       <message name="IDS_EXTENSION_WARNINGS_NETWORK_CONFLICT" desc="Warning message which indicates that two or more extensions tried to modify a network request in a conflicting way and the modification of this extension was ignored">
         This extension failed to modify a network request because the modification conflicted with another extension.
       </message>
 
+      <!-- External extension install alerts -->
+      <!-- TODO(mpcomplete): We may need to change Chrome to
+           PRODUCT_NAME. Leaving it as-is until we finalize
+           these strings. -->
+      <message name="IDS_EXTENSION_EXTERNAL_INSTALL_ALERT" desc="The wrench menu item indicating that a new external extension was installed.">
+        New extension added (<ph name="EXTENSION_NAME">$1<ex>Babylon Toolbar</ex></ph>)

[Jeffrey Yasskin, 2012/10/13 21:17:35]

It would be nice to present a count instead of a single name if multiple
extensions were installed.

[Matt Perry, 2012/10/15 19:13:38]

That should be a pretty occurrence. When it does happen, we just queue them up
and show them one at a time.

[Yoyo Zhou, 2012/10/16 23:28:05]

If this is 

+      </message>
+      <message name="IDS_EXTENSION_EXTERNAL_INSTALL_PROMPT_TITLE" desc="">
+        "<ph name="EXTENSION_NAME">$1<ex>Babylon Toolbar</ex></ph>" added
+      </message>
+      <message name="IDS_EXTENSION_EXTERNAL_INSTALL_PROMPT_HEADING" desc="">
+        While you were out, another program on your computer added an extension to Chrome.
+      </message>
+      <message name="IDS_EXTENSION_EXTERNAL_INSTALL_PROMPT_MAY_CHANGE_CHROME" desc="">
+        This extension may change the way Chrome works.
+      </message>
+      <message name="IDS_EXTENSION_EXTERNAL_INSTALL_PROMPT_ACCEPT_BUTTON" desc="">
+        Enable extension
+      </message>
+      <message name="IDS_EXTENSION_EXTERNAL_INSTALL_PROMPT_ABORT_BUTTON" desc="">
+        Remove from Chrome
+      </message>
+
       <!-- Plugins -->
       <message name="IDS_PLUGINS_TITLE" desc="Title for the chrome://plugins page.">
         Plug-ins
       </message>
       <message name="IDS_PLUGINS_DETAILS_MODE_LINK" desc="Text of the link for details mode.">
         Details
       </message>
       <message name="IDS_PLUGINS_NONE_INSTALLED" desc="Text that lets the user know that no plug-ins are installed.">
         No plug-ins installed.
       </message>
@@ skipping 9414 matching lines @@
 
     <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>