Bug 980248 - DevTools Themes: Extra top border showing up on responsive-container splitters when width > 700px;r=pbrosset

browser/themes/shared/devtools/dark-theme.css

@@ -322,10 +322,7 @@ div.CodeMirror span.eval-text {
 
 .devtools-side-splitter {
   -moz-border-end: 1px solid black;
-}
-
-.devtools-responsive-container > .devtools-side-splitter {
-  border-top: 1px solid black;
+  border-color: black; /* Needed for responsive container at low width. */
 }
 
 .devtools-textinput,

browser/themes/shared/devtools/light-theme.css

@@ -331,10 +331,7 @@ div.CodeMirror span.eval-text {
 
 .devtools-side-splitter {
   -moz-border-end: 1px solid #aaa;
-}
-
-.devtools-responsive-container > .devtools-side-splitter {
-  border-top: 1px solid #aaa;
+  border-color: #aaa; /* Needed for responsive container at low width. */
 }
 
 %include toolbars.inc.css

browser/themes/shared/devtools/widgets.inc.css

@@ -28,7 +28,9 @@
   }
 
   .devtools-responsive-container > .devtools-side-splitter {
-    border: 0;
+    border-width: 0;
+    border-top-width: 1px;
+    border-top-style: solid;
     margin: 0;
     min-height: 3px;
     height: 3px;