Show a custom message in the page info bubble for view-source URLs

Screenshot: https://drive.google.com/file/d/0B9q2eN9gDoUIMGYyeE85Ynk2VGs/view?usp=sharing

BUG=635776
TBR=sdefresne,caitkp

Review-Url: https://codereview.chromium.org/2232453002
Cr-Commit-Position: refs/heads/master@{#412067}
diff --git a/components/pageinfo_strings.grdp b/components/pageinfo_strings.grdp
index af19bec..57d23a9d 100644
--- a/components/pageinfo_strings.grdp
+++ b/components/pageinfo_strings.grdp
@@ -60,6 +60,9 @@
   <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>
+  <message name="IDS_PAGE_INFO_VIEW_SOURCE_PAGE" desc="Message to display in the page info bubble when you are viewing page sources by using |View page source| option from the right click menu.">
+    You are viewing the source of a web 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.">