RFR: JDK-8222251: preflow visitor is not visiting lambda expressions

[Vicente Romero]

Please review fix for [1] at [2]. This patch is fixing a regression 
introduced by [3]. The idea of [3] was to skip the preflow visitor from 
visiting inner classes and lambdas inside an "outer" lambda expression. 
But by passing the "outer" lambda expression to it, the whole lambda 
wasn't being visited. This patch fixes this issue by running the preflow 
visitor on the body of the "outer" lambda expression.

Thanks,
Vicente

[1] https://bugs.openjdk.java.net/browse/JDK-8222251
[2] http://cr.openjdk.java.net/~vromero/8222251/webrev.00/
[3] https://bugs.openjdk.java.net/browse/JDK-8203277