Use a different string and icon for chrome-extension pages in Page Info Bubble.

components/pageinfo_strings.grdp

 <?xml version="1.0" encoding="utf-8"?>
 <grit-part>
   <message name="IDS_PAGE_INFO_HELP_CENTER_LINK" desc="This is the text of the link pointing to the Help Center. This appears at the bottom of the SSL dialog and 'this' refers to the sections within the bubble.">
     What do these mean?
   </message>
   <message name="IDS_PAGE_INFO_SECURITY_TAB_DEPRECATED_SIGNATURE_ALGORITHM_MINOR" desc="The security summary phrase in the page information panel for a security problem where the site's certificate expires in 2016 and contains a SHA1 signature in the chain (as opposed to 2017 or later). Such certificates will not be supported in a future version of Chrome.">
     The certificate for this site expires in 2016, and the certificate chain contains a certificate signed using SHA-1.
   </message>
   <message name="IDS_PAGE_INFO_SECURITY_TAB_DEPRECATED_SIGNATURE_ALGORITHM_MAJOR" desc="The security summary phrase in the page information panel for a security problem where the site's certificate expires in 2017 or later and contains a SHA1 signature in the chain (as opposed to 2016). Such certificates will not be supported in a future version of Chrome.">
     The certificate for this site expires in 2017 or later, and the certificate chain contains a certificate signed using SHA-1.
@@ skipping 39 matching lines @@
   </message>
   <message name="IDS_PAGE_INFO_SECURITY_TAB_UNABLE_TO_CHECK_REVOCATION" desc="The text of the identity section when we were unable to check if the certificate has been revoked.">
     Unable to check whether the certificate has been revoked.
   </message>
   <message name="IDS_PAGE_INFO_SECURITY_TAB_UNKNOWN_PARTY" desc="The default name used when we did not find a principal name.">
     unknown name
   </message>
   <message name="IDS_PAGE_INFO_SECURITY_TAB_WEAK_ENCRYPTION_CONNECTION_TEXT" desc="The text of the connection section when the connection uses weak encryption.">
     Your connection to <ph name="DOMAIN">$1<ex>www.google.com</ex></ph> is encrypted using an obsolete cipher suite.
   </message>
+  <message name="IDS_PAGE_INFO_EXTENSION_PAGE" desc="Message to display in the page info bubble when the page you are on is a chrome-extension:// page. This refers to Chrome extensions.">
+    You are viewing an extension page.
+  </message>
 
   <if expr="not use_titlecase">
     <message name="IDS_PAGEINFO_CERT_INFO_BUTTON" desc="Text of button in the page info that shows the SSL certificate.">
       Certificate information
     </message>
   </if>
   <if expr="use_titlecase">
     <message name="IDS_PAGEINFO_CERT_INFO_BUTTON" desc="In Title Case: Text of button in the page info that shows the SSL certificate.">
       Certificate Information
     </message>
   </if>
 </grit-part>