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

(cherry picked from commit 24e587929f)

Conflicts:

	src/css.js

src/css.js

@@ -292,9 +292,12 @@ 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 ) {
 
-				// Wrapped to prevent IE from throwing errors when 'invalid' values are provided
-				// Fixes bug #5509
+				// Support: IE
+				// Swallow errors from 'invalid' CSS values (#5509)
 				try {
+					// Support: Chrome, Safari
+					// Setting style to blank string required to delete "style: x !important;"
+					style[ name ] = "";
 					style[ name ] = value;
 				} catch(e) {}
 			}