src/vs/platform/keybinding/common/keybindingResolver.ts/KeybindingResolver/_addToLookupMap
class KeybindingResolver:	private _addToLookupMap(item: ResolvedKeybindingItem): void {
		if (!item.command) {
			return;
		}

		let arr = this._lookupMap.get(item.command);
		if (typeof arr === 'undefined') {
			arr = [item];
			this._lookupMap.set(item.command, arr);
		} else {
			arr.push(item);
		}
	}