Method fill

src/animate/Keyframes.js:78–91

()

	}

	fill() {
		this.sort();
		let prevValue;

		for (let time in this.keyframes) {
			const frame = this.keyframes[time];

			for (let key in prevValue) {
				if (frame[key] === undefined) frame[key] = prevValue[key];
			}

			prevValue = frame;
		}
	}

	sort() {
		const cloneObj = {};