Fix #14394: Changing style !important in webkit. Close gh-1385.

src/css.js

@@ -286,6 +286,9 @@ jQuery.extend({
 
 			// If a hook was provided, use that value, otherwise just set the specified value
 			if ( !hooks || !("set" in hooks) || (value = hooks.set( elem, value, extra )) !== undefined ) {
+				// Support: Chrome, Safari
+				// Setting style to blank string required to delete "style: x !important;"
+				style[ name ] = "";
 				style[ name ] = value;
 			}
 

test/unit/css.js

@@ -925,6 +925,12 @@ test( ":visible/:hidden selectors", function() {
 	t( "Is Hidden", "#form input:hidden", ["hidden1","hidden2"] );
 });
 
+test( "Override !important when changing styles (#14394)", function() {
+	expect( 1 );
+	var el = jQuery( "<div style='display: block !important;'></div>" ).css( "display", "none" );
+	equal( el.css( "display" ), "none", "New style replaced !important" );
+});
+
 asyncTest( "Clearing a Cloned Element's Style Shouldn't Clear the Original Element's Style (#8908)", 24, function() {
 	var baseUrl = document.location.href.replace( /([^\/]*)$/, "" ),
 	styles = [{