Polished on side-loaded extension install alert.

chrome/app/google_chrome_strings.grd

 <?xml version="1.0" encoding="UTF-8"?>
 <!-- This file contains definitions of strings that are specific to
 Google Chrome. These strings will be translated for each locale that Google
 Chrome supports. -->
 
 <grit base_dir="." latest_public_release="0" current_release="1"
       source_lang_id="en" enc_check="möl">
   <outputs>
     <output filename="grit/google_chrome_strings.h" type="rc_header">
       <emit emit_type='prepend'></emit>
@@ skipping 567 matching lines @@
           Google Chrome is up to date (<ph name="VERSION">$1<ex>0.1.131</ex></ph>)
         </message>
       </if>
 
       <!-- Extension/App install prompt -->
       <message name="IDS_EXTENSION_INLINE_INSTALL_PROMPT_TITLE" desc="Titlebar of the extension or app inline installation prompt window">
         Add to Chrome
       </message>
 
       <!-- Extension alerts. -->
-      <message name="IDS_EXTENSION_ALERT_ITEM_EXTERNAL" desc="A statement that an external extension has been newly installed. End users have no idea what an 'external' extension is, so we simply call them extensions.">
-The extension "<ph name="EXTENSION_NAME">$1<ex>Gmail Checker</ex></ph>" has been added to Chrome.
+      <message name="IDS_EXTENSION_ALERT_ITEM_EXTERNAL" desc="A statement that an external extension has been newly installed. End users have no idea what an 'external' extension is, so we simply call them extensions. The trailing character is expected to be a newline.">
+The extension "<ph name="EXTENSION_NAME">$1<ex>Gmail Checker</ex></ph>" has been added.
+
 '''
       </message>
 
       <!-- Extension installed bubble -->
       <message name="IDS_EXTENSION_INSTALLED_HEADING" desc="First line in the content area of the extension installed bubble. Instructs that the extension was installed.">
         <ph name="EXTENSION_NAME">$1<ex>Gmail Checker</ex></ph> has been added to Chrome.
       </message>
 
       <!-- chrome://settings/extensions page -->
       <message name="IDS_EXTENSIONS_INCOGNITO_WARNING" desc="Warns the user that Chrome cannot prevent extensions from recording history in incognito mode. Displayed in extensions management UI after an extension is selected to be run in incognito mode.">
@@ skipping 76 matching lines @@
         Chrome Autofill settings
       </message>
 
       <!-- Web Intents -->
       <message name="IDS_INTENT_PICKER_INSTALL_EXTENSION" desc="Text on the button in the web intent picker that installs an extension then uses the extension as an intent service.">
         Add to Chrome
       </message>
     </messages>
   </release>
 </grit>