Don't allow interaction while page loading

Change-Id: I614fe3c90c57511ba392493d683a5b6e8dc169d9

modules/ext.RevisionSlider.DiffPage.js

@@ -4,6 +4,9 @@
 
 	$.extend( DiffPage.prototype, {
 		refresh: function ( oldId, newId ) {
+			$( 'body' )
+				.find( 'table.diff[data-mw=\'interface\']' )
+				.append( '<div id="revision-slider-darkness"></div>' );
 			$.ajax( {
 				url: mw.util.wikiScript( 'index' ),
 				data: {

modules/ext.RevisionSlider.css

@@ -94,3 +94,18 @@
     border-style: solid;
     border-width: 0 10px 10px 10px;
 }
+
+#revision-slider-darkness {
+    background-color: white;
+    filter:alpha(opacity=50); /* IE */
+    opacity: 0.5; /* Safari, Opera */
+    -moz-opacity:0.50; /* FireFox */
+    z-index: 20;
+    height: 100%;
+    width: 100%;
+    background-repeat:no-repeat;
+    background-position:center;
+    position:absolute;
+    top: 0;
+    left: 0;
+}