Revert r21117 as it caused reliability failures....

chrome/utility/utility_thread.cc

Index: chrome/utility/utility_thread.cc
===================================================================
--- chrome/utility/utility_thread.cc	(revision 21215)
+++ chrome/utility/utility_thread.cc	(working copy)
@@ -11,13 +11,22 @@
 #include "chrome/common/extensions/extension_unpacker.h"
 #include "chrome/common/render_messages.h"
 
-UtilityThread::UtilityThread() {
-  ChildProcess::current()->AddRefProcess();
+UtilityThread::UtilityThread() : ChildThread(base::Thread::Options()) {
 }
 
 UtilityThread::~UtilityThread() {
 }
 
+void UtilityThread::Init() {
+  ChildThread::Init();
+  ChildProcess::current()->AddRefProcess();
+}
+
+void UtilityThread::CleanUp() {
+  // Shutdown in reverse of the initialization order.
+  ChildThread::CleanUp();
+}
+
 void UtilityThread::OnControlMessageReceived(const IPC::Message& msg) {
   IPC_BEGIN_MESSAGE_MAP(UtilityThread, msg)
     IPC_MESSAGE_HANDLER(UtilityMsg_UnpackExtension, OnUnpackExtension)