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 571 matching lines @@
         </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.
+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 71 matching lines @@
       <message name="IDS_SYNC_PROMO_V_LEARN_MORE" desc="Learn more link at the bottom of the sync promo.">
         See <ph name="BEGIN_LINK">&lt;a target="_blank" href="$1"&gt;</ph>more benefits<ph name="END_LINK">&lt;/a&gt;</ph> of signing in to Chrome.
       </message>
 
       <message name="IDS_AUTOFILL_OPTIONS_POPUP" desc="The value of the Autofill options menu entry.">
         Chrome Autofill settings
       </message>
     </messages>
   </release>
 </grit>