Update NetLog to be thread safe.

chrome/browser/io_thread.cc

Index: chrome/browser/io_thread.cc
===================================================================
--- chrome/browser/io_thread.cc	(revision 65207)
+++ chrome/browser/io_thread.cc	(working copy)
@@ -206,8 +206,9 @@
 
 IOThread::Globals::~Globals() {}
 
-IOThread::IOThread()
-    : BrowserProcessSubThread(BrowserThread::IO),
+IOThread::IOThread(ChromeNetLog* net_log)
+    : net_log_(net_log),
+      BrowserProcessSubThread(BrowserThread::IO),
       globals_(NULL),
       speculative_interceptor_(NULL),
       predictor_(NULL) {}
@@ -224,6 +225,10 @@
   return globals_;
 }
 
+ChromeNetLog* IOThread::net_log() {
+  return net_log_;
+}
+
 void IOThread::InitNetworkPredictor(
     bool prefetching_enabled,
     base::TimeDelta max_dns_queue_delay,
@@ -275,16 +280,14 @@
   DCHECK(!globals_);
   globals_ = new Globals;
 
-  globals_->net_log.reset(new ChromeNetLog());
-
   // Add an observer that will emit network change events to the ChromeNetLog.
   // Assuming NetworkChangeNotifier dispatches in FIFO order, we should be
   // logging the network change before other IO thread consumers respond to it.
   network_change_observer_.reset(
-      new LoggingNetworkChangeObserver(globals_->net_log.get()));
+      new LoggingNetworkChangeObserver(net_log_));
 
   globals_->host_resolver.reset(
-      CreateGlobalHostResolver(globals_->net_log.get()));
+      CreateGlobalHostResolver(net_log_));
   globals_->dnsrr_resolver.reset(new net::DnsRRResolver);
   globals_->http_auth_handler_factory.reset(CreateDefaultAuthHandlerFactory(
       globals_->host_resolver.get()));
@@ -332,10 +335,6 @@
     (*it)->Cancel();
   }
 
-  // We will delete the NetLog as part of CleanUpAfterMessageLoopDestruction()
-  // in case any of the message loop destruction observers try to access it.
-  deferred_net_log_to_delete_.reset(globals_->net_log.release());
-
   delete globals_;
   globals_ = NULL;
 
@@ -343,11 +342,6 @@
 }
 
 void IOThread::CleanUpAfterMessageLoopDestruction() {
-  // TODO(eroman): get rid of this special case for 39723. If we could instead
-  // have a method that runs after the message loop destruction obsevers have
-  // run, but before the message loop itself is destroyed, we could safely
-  // combine the two cleanups.
-  deferred_net_log_to_delete_.reset();
   BrowserProcessSubThread::CleanUpAfterMessageLoopDestruction();
 
   // URLRequest instances must NOT outlive the IO thread.
@@ -440,5 +434,5 @@
   // Clear all of the passively logged data.
   // TODO(eroman): this is a bit heavy handed, really all we need to do is
   //               clear the data pertaining to off the record context.
-  globals_->net_log->passive_collector()->Clear();
+  net_log_->passive_collector()->Clear();
 }