Have different text for apps and regular extensions in some more places.

chrome/app/chromium_strings.grd

Index: chrome/app/chromium_strings.grd
diff --git a/chrome/app/chromium_strings.grd b/chrome/app/chromium_strings.grd
index 43bb43a72099e8fe18d0ae8619f3dd27458e1eef..91d440fb0e0836f7421c90efe8972007c94bfee4 100644
--- a/chrome/app/chromium_strings.grd
+++ b/chrome/app/chromium_strings.grd
@@ -703,13 +703,6 @@ For Chromium, processes used to display diagnostics information (such as this "a
         Add to Chromium
       </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 trailing character must 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 Chromium.