some more sidebar skinnability stuff (19557) and fix assert and non-visible sidebar panel header in preview (39632)

xpfe/components/sidebar/resources/preview.xul

@@ -19,7 +19,7 @@
 -->
 
 <?xml-stylesheet href="chrome://communicator/skin/" type="text/css"?>
-<?xml-stylesheet href="chrome://communicator/skin/sidebar/sidebarOverlay.css"
+<?xml-stylesheet href="chrome://communicator/skin/sidebar/sidebar.css"
   type="text/css"?>
 <?xml-stylesheet href="chrome://communicator/skin/sidebar/preview.css"
   type="text/css"?>

xpfe/components/sidebar/resources/sidebarBindings.xml

@@ -30,14 +30,14 @@
   </binding>
 
   <binding id="sidebar-header-box" extends="xul:box">
-    <content>
+    <content autostretch="never" valign="middle">
       <xul:text inherits="value,crop" crop="right" flex="1"/>
       <xul:box><children/></xul:box>
     </content>
   </binding>  
 
   <binding id="sidebar-header-splitter" extends="xul:splitter">
-    <content>
+    <content autostretch="never" valign="middle">
       <xul:text inherits="value,crop" crop="right" flex="1"/>
       <xul:box><children/></xul:box>
     </content>

xpfe/components/sidebar/resources/sidebarOverlay.xul

@@ -65,7 +65,7 @@
             exclude="rdf:http://home.netscape.com/NC-rdf#exclude"
             hidden="true"/>
           <box uri="rdf:*" flex='1*' hidden="true" orient="vertical">
-            <box flex='1' orient="vertical">
+            <box flex='1' orient="vertical" class="iframe-panel">
               <box orient="horizontal" flex="1" autostretch="never">
                 <image class="image-panel-loading"/>
                 <text class="text-panel-loading"
@@ -88,7 +88,7 @@
 
   <!-- Splitter on the right of sidebar -->
   <splitter id="sidebar-splitter" collapse="before" persist="state hidden"
-    class="chromeclass-extrachrome sidebar-splitter"
+    class="chromeclass-extrachrome sidebar-splitter" autostretch="never" orient="vertical"
     onmouseup="SidebarFinishDrag();">
     <grippy class="sidebar-splitter-grippy" onclick="SidebarExpandCollapse();"/>
   </splitter>