src/vs/editor/browser/editorExtensions.ts/MultiCommand/addImplementation
class MultiCommand:	public addImplementation(priority: number, name: string, implementation: CommandImplementation): IDisposable {
		this._implementations.push({ priority, name, implementation });
		this._implementations.sort((a, b) => b.priority - a.priority);
		return {
			dispose: () => {
				for (let i = 0; i < this._implementations.length; i++) {
					if (this._implementations[i].implementation === implementation) {
						this._implementations.splice(i, 1);
						return;
					}
				}
			}
		};
	}