fox for #168937. need to set width of messengerBox so that the splitter doesn't jump

around for new (and existing) users.  this is fallout for the sidebar being removed
from the three pane.  r/sr=bienvenu

mailnews/base/resources/content/mail3PaneWindowVertLayout.xul

@@ -154,7 +154,7 @@ Rights Reserved.
           <grippy/>
         </splitter>
 
-        <hbox id="mail3PaneVertLayoutBox" persist="collapsed width" flex="2">
+        <hbox id="messengerBox" persist="collapsed width" flex="2">
           <vbox id="searchAndthreadpaneBox" persist="width" flex ="1">
            <vbox id="messagesBox" flex="1">
             <hbox id="searchBox"/>

mailnews/base/resources/content/msgMail3PaneWindow.js

@@ -566,6 +566,15 @@ function OnLoadMessenger()
 
   gNotifyDefaultInboxLoadedOnStartup = true;
 
+  // fix for #168937.  now that we don't have a sidebar
+  // users who haven't moved the splitter will
+  // see it jump around
+  var messengerBox = document.getElementById("messengerBox");
+  if (!messengerBox.getAttribute("width")) {
+    messengerBox.setAttribute("width","500px");
+  }
+
+
   //Set focus to the Thread Pane the first time the window is opened.
   SetFocusThreadPane();
 }