6637203: Classunloading messages go to stdout rather than Xloggc file, causing...

6637203: Classunloading messages go to stdout rather than Xloggc file, causing hangs when stdout is closed
Summary: Decoupled TraceClassUnloading from verbose:gc, JVMTI_VERBOSE_GC and PrintGC[Details], making it settable in a manner identical to TraceClassLoading. Reverted an inadvertent change of TraceClassUnloading output in a previous changeset from gclog back to tty.
Reviewed-by: coleenp, dholmes, jmasa, poonam

src/share/vm/prims/jvmtiEnv.cpp

@@ -592,7 +592,6 @@ JvmtiEnv::SetVerboseFlag(jvmtiVerboseFlag flag, jboolean value) {
     break;
   case JVMTI_VERBOSE_GC:
     PrintGC = value != 0;
-    TraceClassUnloading = value != 0;
     break;
   case JVMTI_VERBOSE_JNI:
     PrintJNIResolving = value != 0;

src/share/vm/runtime/arguments.cpp

@@ -1866,7 +1866,6 @@ jint Arguments::parse_each_vm_init_arg(const JavaVMInitArgs* args,
         FLAG_SET_CMDLINE(bool, TraceClassUnloading, true);
       } else if (!strcmp(tail, ":gc")) {
         FLAG_SET_CMDLINE(bool, PrintGC, true);
-        FLAG_SET_CMDLINE(bool, TraceClassUnloading, true);
       } else if (!strcmp(tail, ":jni")) {
         FLAG_SET_CMDLINE(bool, PrintJNIResolving, true);
       }
@@ -2720,9 +2719,6 @@ jint Arguments::parse(const JavaVMInitArgs* args) {
   if (PrintGCDetails) {
     // Turn on -verbose:gc options as well
     PrintGC = true;
-    if (FLAG_IS_DEFAULT(TraceClassUnloading)) {
-      TraceClassUnloading = true;
-    }
   }
 
 #if defined(_LP64) && defined(COMPILER1)

src/share/vm/services/classLoadingService.cpp

@@ -128,7 +128,7 @@ void ClassLoadingService::notify_class_unloaded(instanceKlass* k) {
 
   if (TraceClassUnloading) {
     ResourceMark rm;
-    gclog_or_tty->print_cr("[Unloading class %s]", k->external_name());
+    tty->print_cr("[Unloading class %s]", k->external_name());
   }
 }