src/vs/editor/browser/controller/mouseTarget.ts/MouseTargetFactory/mouseTargetIsWidget
class MouseTargetFactory:	public mouseTargetIsWidget(e: EditorMouseEvent): boolean {
		const t = <Element>e.target;
		const path = PartFingerprints.collect(t, this._viewHelper.viewDomNode);

		// Is it a content widget?
		if (ElementPath.isChildOfContentWidgets(path) || ElementPath.isChildOfOverflowingContentWidgets(path)) {
			return true;
		}

		// Is it an overlay widget?
		if (ElementPath.isChildOfOverlayWidgets(path)) {
			return true;
		}

		return false;
	}