src/vs/base/browser/touch.ts/Gesture/onTouchStart
class Gesture:	private onTouchStart(e: TouchEvent): void {
		const timestamp = Date.now(); // use Date.now() because on FF e.timeStamp is not epoch based.

		if (this.handle) {
			this.handle.dispose();
			this.handle = null;
		}

		for (let i = 0, len = e.targetTouches.length; i < len; i++) {
			const touch = e.targetTouches.item(i);

			this.activeTouches[touch.identifier] = {
				id: touch.identifier,
				initialTarget: touch.target,
				initialTimeStamp: timestamp,
				initialPageX: touch.pageX,
				initialPageY: touch.pageY,
				rollingTimestamps: [timestamp],
				rollingPageX: [touch.pageX],
				rollingPageY: [touch.pageY]
			};

			const evt = this.newGestureEvent(EventType.Start, touch.target);
			evt.pageX = touch.pageX;
			evt.pageY = touch.pageY;
			this.dispatchEvent(evt);
		}

		if (this.dispatched) {
			e.preventDefault();
			e.stopPropagation();
			this.dispatched = false;
		}
	}