Add notice when parallel recompilation is disabled by tracing.

src/v8.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 254 matching lines @@
 
 
 void V8::InitializeOncePerProcessImpl() {
   FlagList::EnforceFlagImplications();
   if (FLAG_stress_compaction) {
     FLAG_force_marking_deque_overflows = true;
     FLAG_gc_global = true;
     FLAG_max_new_space_size = (1 << (kPageSizeBits - 10)) * 2;
   }
 
-  if (FLAG_trace_hydrogen || FLAG_trace_hydrogen_stubs) {
-    // Tracing hydrogen do not work with parallel recompilation.
+  if (FLAG_parallel_recompilation &&
+      (FLAG_trace_hydrogen || FLAG_trace_hydrogen_stubs)) {
     FLAG_parallel_recompilation = false;
+    PrintF("Parallel recompilation has been disabled for tracing.\n");
   }
 
   if (FLAG_sweeper_threads <= 0) {
     if (FLAG_concurrent_sweeping) {
       FLAG_sweeper_threads = SystemThreadManager::
           NumberOfParallelSystemThreads(
               SystemThreadManager::CONCURRENT_SWEEPING);
     } else if (FLAG_parallel_sweeping) {
       FLAG_sweeper_threads = SystemThreadManager::
           NumberOfParallelSystemThreads(
@@ skipping 39 matching lines @@
   ExternalReference::SetUp();
   Bootstrapper::InitializeOncePerProcess();
 }
 
 
 void V8::InitializeOncePerProcess() {
   CallOnce(&init_once, &InitializeOncePerProcessImpl);
 }
 
 } }  // namespace v8::internal