Bug 947257 - Splitters have a dark squary sort of thing in their center. r=paul

browser/themes/shared/devtools/common.css

@@ -24,6 +24,7 @@
 /* Splitters */
 .devtools-horizontal-splitter {
   -moz-appearance: none;
+  background-image: none;
   border-top: 1px solid black;
   border-bottom-width: 0;
   min-height: 3px;
@@ -34,6 +35,7 @@
 
 .devtools-side-splitter {
   -moz-appearance: none;
+  background-image: none;
   border: 0;
   -moz-border-start: 1px solid black;
   min-width: 0;