Update NetLog to be thread safe.

chrome/browser/debugger/devtools_netlog_observer.cc

Index: chrome/browser/debugger/devtools_netlog_observer.cc
===================================================================
--- chrome/browser/debugger/devtools_netlog_observer.cc	(revision 65207)
+++ chrome/browser/debugger/devtools_netlog_observer.cc	(working copy)
@@ -41,6 +41,10 @@
                                         const net::NetLog::Source& source,
                                         net::NetLog::EventPhase phase,
                                         net::NetLog::EventParameters* params) {
+  // The events that the Observer is interested in only occur on the IO thread.
+  if (!BrowserThread::CurrentlyOn(BrowserThread::IO))
+    return;
+
   if (type == net::NetLog::TYPE_URL_REQUEST_START_JOB) {
     if (phase != net::NetLog::PHASE_BEGIN)
       return;
@@ -100,7 +104,7 @@
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
   DCHECK(!instance_);
 
-  instance_ = new DevToolsNetLogObserver(io_thread->globals()->net_log.get());
+  instance_ = new DevToolsNetLogObserver(io_thread->net_log());
 }
 
 void DevToolsNetLogObserver::Detach() {