Eliminates need for an IE6/7-specific workaround class, as well as ad…

…ditional scripting.

css/structure/jquery.mobile.popup.css

@@ -1,19 +1,15 @@
 .ui-popup-screen {
+	background-image: url(data:image/gif;base64,R0lGODlhAQABAID/AMDAwAAAACH5BAEAAAAALAAAAAABAAEAAAICRAEAOw==); /* Necessary to set some form of background to ensure element is clickable in IE6/7. While legacy IE won’t understand the data-URI’d image, it ensures no additional requests occur in all other browsers with little overhead. */
 	top: 0px;
 	left: 0px;
 	right: 0px;
 	bottom: 1px;
 	position: absolute;
-	filter: Alpha(Opacity=50);
+	filter: Alpha(Opacity=0);
 	opacity: 0;
 	z-index: 1099;
 }
 
-.ui-popup-screen-background-hack {
-	background-color: black;
-	filter: Alpha(Opacity=0);
-}
-
 @-webkit-keyframes popup-fadein {
     from { opacity: 0; }
     to { opacity: 0.5; }
@@ -36,12 +32,14 @@
 
 .ui-popup-screen.fade.in {
 	opacity: 0.5;
+	filter: Alpha(Opacity=50);
 	-webkit-animation-name: popup-fadein;
 	-moz-animation-name: popup-fadein;
 }
 
 .ui-popup-screen.fade.out {
 	opacity: 0;
+	filter: Alpha(Opacity=0);
 	-webkit-animation-name: popup-fadeout;
 	-moz-animation-name: popup-fadeout;
 }

js/widgets/popup.js

@@ -222,15 +222,6 @@ define( [ "jquery",
 		_setOverlayTheme: function( value ) {
 			this._applyTheme( this._ui.screen, value, "overlay" );
 
-			if ( $.mobile.browser.ie ) {
-				this._ui.screen.toggleClass(
-					"ui-popup-screen-background-hack",
-					( this._ui.screen.css( "background-color" ) === "transparent" &&
-						this._ui.screen.css( "background-image" ) === "none" &&
-						( this._ui.screen.css( "background" ) === undefined ||
-							this._ui.screen.css( "background" ) === "" ) ) );
-			}
-
 			if ( this._isOpen ) {
 				this._ui.screen.addClass( "in" );
 			}