src/vs/workbench/contrib/bulkEdit/browser/preview/bulkEditPreview.ts/CheckedStates/updateChecked
class CheckedStates:	updateChecked(obj: T, value: boolean): void {
		const valueNow = this._states.get(obj);
		if (valueNow === value) {
			return;
		}
		if (valueNow === undefined) {
			if (value) {
				this._checkedCount += 1;
			}
		} else {
			if (value) {
				this._checkedCount += 1;
			} else {
				this._checkedCount -= 1;
			}
		}
		this._states.set(obj, value);
		this._onDidChange.fire(obj);
	}