Reland Extension Installed InfoBubble

chrome/common/extensions/docs/static/pageAction.html

Index: chrome/common/extensions/docs/static/pageAction.html
diff --git a/chrome/common/extensions/docs/static/pageAction.html b/chrome/common/extensions/docs/static/pageAction.html
index 204048df2a89f2670ed1d3ddc509fe049f116fdb..26836613cbf0f9fbfe16a605f4f9e1838c818c06 100755
--- a/chrome/common/extensions/docs/static/pageAction.html
+++ b/chrome/common/extensions/docs/static/pageAction.html
@@ -49,6 +49,12 @@ like this:
   reserves a slot for your page action
   in the address bar.</p>
 
+<p>
+Although the "default_icon" is optional, it's a good idea to provide one.
+When users install your extension, if you have set a default icon, it can
+be previewed to the user so they know what to look for when your page action
+is active for a given page.</p>
+
 <h2 id="ui">Parts of the UI</h2>
 
 <p>