Remove button in Smart Browsing pref pane should be context disabled.

b=119768; r=morse; sr=hewitt

xpfe/components/prefwindow/resources/content/pref-smart_browsing.js

@@ -75,6 +75,7 @@ function removeDomain()
   }
   selectFirstCell();
   rebuildPrefValue();
+  toggleRemoveButton();
 }
     
 function rebuildPrefValue()
@@ -126,9 +127,20 @@ function doButtonEnabling()
   if (parent.hPrefWindow.getPrefIsLocked(addDomain.getAttribute("prefstring")))
     addDomain.disabled = true;
     
+  toggleRemoveButton();
   toggleAutoCompleteAdvancedButton();
 }  
 
+function toggleRemoveButton()
+{
+  var domains = document.getElementById("disabledKids");
+  var removeButton = document.getElementById("removeDomain");
+  if (domains.childNodes.length == 0)
+    removeButton.disabled = true;
+  else
+    removeButton.disabled = false; 
+}
+
 function moreInfo()
 {
   var browserURL = null;

xpfe/components/prefwindow/resources/content/pref-smart_browsing.xul

@@ -83,7 +83,8 @@
             <treechildren id="disabledKids" flex="1"/>
           </tree>
           <vbox align="center">
-            <button id="removeDomain" label="&removeDomain.label;" accesskey="&removeDomain.accesskey;"
+            <button id="removeDomain" label="&removeDomain.label;" 
+                    accesskey="&removeDomain.accesskey;" disabled="true"
                     oncommand="removeDomain();" prefstring="pref.browser.smartbrowsing.disable_button.remove"/>
           </vbox>
         </row>