RFR: 8278123: serviceability/dcmd/vm/ClassLoaderStatsTest.java failing with java.lang.AssertionError: Should have a hidden class

[Leonid Mesnik]

The test failed if GC happens somewhere between
Class<?> c = Class.forName("TestClass", true, dummyloader);
and
OutputAnalyzer output = executor.execute("VM.classloader_stats");

The fix is to make hc static as Chris proposed. 

To verfiy fix I add System.gc() before executor.execute("VM.classloader_stats");

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Commit messages:
 - fix

Changes: https://git.openjdk.java.net/jdk/pull/8438/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8438&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8278123
  Stats: 4 lines in 1 file changed: 1 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8438.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8438/head:pull/8438

PR: https://git.openjdk.java.net/jdk/pull/8438