fixing bug 54885-alternative mailnews 3-pane forgets sizes. r=bhuvan sr=sspitzer

mailnews/base/resources/content/mail3PaneWindowVertLayout.xul

@@ -136,22 +136,23 @@ Rights Reserved.
 
 
   <box orient="horizontal" style="height:100px" flex="1">
-    <box id="sidebar-box"/>
+    <box id="sidebar-box" persist="collapsed width"/>
     <splitter id="sidebar-splitter" state="collapsed"/>
           
     <box orient="vertical" flex="1">
-      <box align ="horizontal" persist="height" flex="1">
-        <box flex="1">
+      <box id="mail3PaneVertLayoutBox" orient="horizontal" persist="collapsed height" flex="1">
         <tree id="folderTree" flex="1" style="width:0px;" context="folderPaneContext" persist="collapsed width"/>
-         <splitter id="gray_vertical_splitter" collapse="before"  persist="state"/>
-         <box id="threadpaneBox" flex="2">
+        <splitter id="gray_vertical_splitter" collapse="before"  persist="state">
+          <grippy/>
+        </splitter>
+
+        <box id="threadpaneBox" flex="2" persist="width">
           <outliner id="threadOutliner" flex="2" persist="width" style="width:0px" context="threadPaneContext" class="window-focusborder" focusring="false"/>
         </box>
-         <box id="accountCentralBox" flex="2"> 
+        <box id="accountCentralBox" flex="2" persist="width"> 
           <iframe name="accountCentralPane" style="width:0px;" flex="1" src="about:blank"/>
         </box>
       </box>
-      </box>
       <!-- if you change this id, please change GetThreadAndMessagePaneSplitter() and MsgToggleMessagePane() -->
       <splitter id="threadpane-splitter" collapse="after" persist="state"
          orient="vertical" autostretch="never">