[11u] RFR (XS) 8262465: Very long compilation times and high memory consumption in C2 debug builds

[Aleksey Shipilev]

Original bug:
   https://bugs.openjdk.java.net/browse/JDK-8262465
   https://git.openjdk.java.net/jdk/commit/2da882c0

This effectively guards the verification block with C2 testing flag. Unfortunately, the patch does 
not apply cleanly due to protected block being a bit different.

11u variant:
   https://cr.openjdk.java.net/~shade/8262465/webrev.11u.01/

Testing: tier{1,2}

-- 
Thanks,
-Aleksey