src/vs/workbench/contrib/debug/common/debugModel.ts/DebugModel/addWatchExpression
class DebugModel:	addWatchExpression(name?: string): IExpression {
		const we = new Expression(name || '');
		this.watchExpressions.push(we);
		this._onDidChangeWatchExpressions.fire(we);

		return we;
	}