Produces linear gradient definition used in early Webkit
implementations
@param {Object} gradient Parsed gradient
@returns {String}
function(gradient) {
			if (_.isString(gradient))
				gradient = this.parse(gradient);
			
			if (!gradient)
				return null;
			
			var colorStops = _.map(gradient.colorStops, _.clone);
			
			// normalize color-stops position
			_.each(colorStops, function(cs) {
				if (!('position' in cs)) // implied position
					return;
				
				if (~cs.position.indexOf('.') || cs.unit == '%') {
					cs.position = parseFloat(cs.position) / (cs.unit == '%' ? 100 : 1);
				} else {
					throw "Can't convert color stop '" + (cs.position + (cs.unit || '')) + "'";
				}
			});
			
			fillImpliedPositions(colorStops);
			
			// transform color-stops into string representation
			colorStops = _.map(colorStops, function(cs, i) {
				if (!cs.position && !i)
					return 'from(' + cs.color + ')';
				
				if (cs.position == 1 && i == colorStops.length - 1)
					return 'to(' + cs.color + ')';
				
				return 'color-stop(' + (cs.position.toFixed(2).replace(/\.?0+$/, '')) + ', ' + cs.color + ')';
			});
			
			return '-webkit-gradient(linear, ' 
				+ oldWebkitDirection(gradient.direction)
				+ ', '
				+ colorStops.join(', ')
				+ ')';
		}