New post-sideload UI:

chrome/app/generated_resources.grd

Index: chrome/app/generated_resources.grd
diff --git a/chrome/app/generated_resources.grd b/chrome/app/generated_resources.grd
index 3e5e642642eda94f403b7d9c3d7b078cd558d396..04817bc89a41e3d53762fa1d5540c5d23bbf69f6 100644
--- a/chrome/app/generated_resources.grd
+++ b/chrome/app/generated_resources.grd
@@ -5301,7 +5301,7 @@ Keep your key file in a safe place. You will need it to create new versions of y
       </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">
@@ -5314,6 +5314,26 @@ Keep your key file in a safe place. You will need it to create new versions of y
         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, 2012/10/17 07:08:56]

Should be rare, and it's certainly fair to change the spelling in a subsequent
change if the UI folks agree with me.

+      </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. 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