code clean up for buddy icon in ab card pane. r/sr=bienvenu

mailnews/addrbook/resources/content/abCardViewOverlay.js

@@ -30,12 +30,9 @@
 var gPrefs = Components.classes["@mozilla.org/preferences-service;1"];
 gPrefs = gPrefs.getService();
 gPrefs = gPrefs.QueryInterface(Components.interfaces.nsIPrefBranch);
-	
-var gProfile = Components.classes["@mozilla.org/profile/manager;1"].getService(Components.interfaces.nsIProfileInternal);
 
-var gProfileDirURL = Components.classes["@mozilla.org/network/standard-url;1"].createInstance(Components.interfaces.nsIFileURL);
-gProfileDirURL.file = gProfile.getProfileDir(gProfile.currentProfile);
-var gIconFileURL = Components.classes["@mozilla.org/network/standard-url;1"].createInstance(Components.interfaces.nsIFileURL);
+var gProfileDirURL;
+var gIconFileURL;
 
 var gMapItURLFormat = gPrefs.getComplexValue("mail.addr_book.mapit_url.format", 
                                               Components.interfaces.nsIPrefLocalizedString).data;
@@ -339,11 +336,22 @@ function setBuddyIcon(card, buddyIcon)
   try {
     var myScreenName = gPrefs.getCharPref("aim.session.screenname");
     if (myScreenName && card.primaryEmail) {
+      if (!gProfileDirURL) {
+        // lazily create these file urls, and keep them around
+        gProfileDirURL = Components.classes["@mozilla.org/network/standard-url;1"].createInstance(Components.interfaces.nsIFileURL);
+        gIconFileURL = Components.classes["@mozilla.org/network/standard-url;1"].createInstance(Components.interfaces.nsIFileURL);
+        var profile = Components.classes["@mozilla.org/profile/manager;1"].getService(Components.interfaces.nsIProfileInternal);
+        gProfileDirURL.file = profile.getProfileDir(profile.currentProfile);
+      }
+
+      // if we did have a buddy icon on disk for this screenname, this would be the file url spec for it
       var iconURLStr = gProfileDirURL.spec + "/NIM/" + myScreenName + "/picture/" + card.aimScreenName + ".gif";
 
       // check if the file exists
       gIconFileURL.spec = iconURLStr;
             
+      // check if the file exists
+      // is this a perf hit?  (how expensive is stat()?)
       if (gIconFileURL.file.exists()) {
         buddyIcon.setAttribute("src", iconURLStr);
         return true;