Bug 194876 Want tree attribute for column picker tooltip text r=varga sr=sspitzer

mailnews/base/resources/content/threadPane.xul

@@ -38,7 +38,7 @@ Contributors:
 <tree id="threadTree" flex="1" enableColumnDrag="true" _selectDelay="500" class="plain" disableKeyNavigation="true"
     onkeypress="ThreadPaneKeyPress(event);"
     onselect="ThreadPaneSelectionChanged();">
-  <treecols>
+  <treecols pickertooltiptext="&columnChooser.tooltip;">
     <treecol id="threadCol" persist="hidden ordinal" fixed="true" cycler="true" class="treecol-image threadColumnHeader" currentView="unthreaded"
              display="&threadColumn.label;" tooltiptext="&threadColumn.tooltip;"/>
     <splitter class="tree-splitter"/>

mailnews/base/resources/locale/en-US/threadpane.dtd

@@ -37,6 +37,7 @@ Rights Reserved.
 <!ENTITY idColumn.label "ID">
 
 <!--Tooltips-->
+<!ENTITY columnChooser.tooltip "Click to select columns to display">
 <!ENTITY threadColumn.tooltip "Click to display message threads"> 
 <!ENTITY senderColumn.tooltip "Click to sort by sender">
 <!ENTITY subjectColumn.tooltip "Click to sort by subject">

xpfe/global/resources/content/bindings/tree.xml

@@ -637,7 +637,7 @@
   <binding id="treecols" extends="chrome://global/content/bindings/tree.xml#tree-base">
     <content>
       <children includes="treecol|splitter"/>
-      <xul:treecolpicker class="treecol-image" fixed="true" ordinal="2147483647"/>
+      <xul:treecolpicker class="treecol-image" fixed="true" ordinal="2147483647" xbl:inherits="tooltiptext=pickertooltiptext"/>
     </content>
     <implementation implements="nsIAccessibleProvider">
       <property name="accessible">