Make text for sidebar-header-box and sidebar-header-splitter flexible so it can be collapsed.

xpfe/global/resources/content/globalBindings.xml

@@ -26,16 +26,14 @@
 
   <binding id="sidebar-header-box" extends="xul:box">
     <content>
-      <xul:text inherits="value,crop" crop="right" />
-      <xul:spring flex="100%"/>
+      <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>
-      <xul:text inherits="value,crop" crop="right" />
-      <xul:spring flex="100%"/>
+      <xul:text inherits="value,crop" crop="right" flex="1"/>
       <xul:box><children/></xul:box>
     </content>
   </binding>