Enable preemption in d8.

src/top.cc

 // Copyright 2006-2008 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 19 matching lines @@
 #include "api.h"
 #include "bootstrapper.h"
 #include "debug.h"
 #include "execution.h"
 #include "string-stream.h"
 #include "platform.h"
 
 namespace v8 { namespace internal {
 
 ThreadLocalTop Top::thread_local_;
-Mutex* Top::break_access_;
+Mutex* Top::break_access_ = OS::CreateMutex();
 StackFrame::Id Top::break_frame_id_;
 int Top::break_count_;
 int Top::break_id_;
 
 NoAllocationStringAllocator* preallocated_message_space = NULL;
 
 Address top_addresses[] = {
 #define C(name) reinterpret_cast<Address>(Top::name()),
     TOP_ADDRESS_LIST(C)
 #undef C
@@ skipping 167 matching lines @@
 char* PreallocatedMemoryThread::data_ = NULL;
 unsigned PreallocatedMemoryThread::length_ = 0;
 
 static bool initialized = false;
 
 void Top::Initialize() {
   CHECK(!initialized);
 
   InitializeThreadLocal();
 
-  break_access_ = OS::CreateMutex();
   break_frame_id_ = StackFrame::NO_ID;
   break_count_ = 0;
   break_id_ = 0;
 
   // Only preallocate on the first initialization.
   if (FLAG_preallocate_message_memory && (preallocated_message_space == NULL)) {
     // Start the thread which will set aside some memory.
     PreallocatedMemoryThread::StartThread();
     preallocated_message_space =
         new NoAllocationStringAllocator(PreallocatedMemoryThread::data(),
@@ skipping 718 matching lines @@
   Top::break_access_->Lock();
 }
 
 
 ExecutionAccess::~ExecutionAccess() {
   Top::break_access_->Unlock();
 }
 
 
 } }  // namespace v8::internal