src/vs/workbench/contrib/debug/common/debugModel.ts/Thread/clearCallStack
class Thread:	clearCallStack(): void {
		if (this.callStack.length) {
			this.staleCallStack = this.callStack;
		}
		this.callStack = [];
		this.callStackCancellationTokens.forEach(c => c.dispose(true));
		this.callStackCancellationTokens = [];
	}