Add rule to collapse splitter siblings when collapsed='true'. Eventually we may want to make this rule more general (by taking off 'box >'). Bug 29813. r=evaughan,mcafee a=jevering r=hyatt

xpfe/global/resources/skin/global.css

@@ -533,6 +533,10 @@ splitter[state="dragging"]
    background-color: gray;
 }
 
+box > *[collapsed="true"] {
+  visibility: collapse;
+}
+
 grippy{
 	margin: 0px;
 	border: 2px solid #003366;
@@ -1426,7 +1430,7 @@ deck.tabpanel, tabpanel {
  **********************************/
 
 /**
- * textab folder lookalike e.g. for sidebar panel headers
+ * texttab folder lookalike e.g. for sidebar panel headers
  */
 
 box.texttab{