[12]RFR 8205399 : Set node color on pinned HashMap.TreeNode deletion

[Brent Christian]

Hi,

Please review the following fix.

Bug: https://bugs.openjdk.java.net/browse/JDK-8205399
Webrev: http://cr.openjdk.java.net/~bchristi/8205399/webrev01/

The vmTestbase/vm/gc/containers/Combination05/TestDescription.java test, 
which does random adds and removes (via Iterator), has been failing 
intermittently with an AssertionError.

I tracked down a couple sequences of operations that trigger the 
assertion.  Sufficient HashMap collisions convert a bin to a tree, and 
then values are deleted using Iterator.remove() (pinned node deletion).

The condition that fails in HashMap.TreeNode.checkInvariants() is:

   if (t.red && tl != null && tl.red && tr != null && tr.red)

A red TreeNode should not have two red children.

Many thanks to Doug Lea for providing the fix for the HashMap red/black 
tree code.  The root node color needs to be set in this case.

Thanks,
-Brent