Parses gradient definition
@param {String} gradient
@returns {Object}
function(gradient) {
			var result = null;
			require('utils').trim(gradient).replace(/^([\w\-]+)\((.+?)\)$/, function(str, type, definition) {
				// remove vendor prefix
				type = type.toLowerCase().replace(/^\-[a-z]+\-/, '');
				if (type == 'linear-gradient' || type == 'lg') {
					result = parseLinearGradient(definition);
					return '';
				}
				
				return str;
			});
			
			return result;
		}