Update NetLog to be thread safe.

chrome/browser/net/load_timing_observer.h

Index: chrome/browser/net/load_timing_observer.h
===================================================================
--- chrome/browser/net/load_timing_observer.h	(revision 65207)
+++ chrome/browser/net/load_timing_observer.h	(working copy)
@@ -43,8 +43,6 @@
   LoadTimingObserver();
   ~LoadTimingObserver();
 
-  URLRequestRecord* GetURLRequestRecord(uint32 source_id);
-
   // Observer implementation:
   virtual void OnAddEntry(net::NetLog::EventType type,
                           const base::TimeTicks& time,
@@ -61,6 +59,8 @@
   FRIEND_TEST_ALL_PREFIXES(LoadTimingObserverTest,
                            SocketRecord);
 
+  // Note that |lock_| must be acquired before calling all of the following
+  // functions.
   void OnAddURLRequestEntry(net::NetLog::EventType type,
                             const base::TimeTicks& time,
                             const net::NetLog::Source& source,
@@ -79,9 +79,12 @@
                         net::NetLog::EventPhase phase,
                         net::NetLog::EventParameters* params);
 
-  URLRequestRecord* CreateURLRequestRecord(uint32 source_id);
-  void DeleteURLRequestRecord(uint32 source_id);
+  // |lock_| must be aquired for as long as the returned |URLRequestRecord*|
+  // is in use.
+  URLRequestRecord* GetURLRequestRecord(uint32 source_id);
 
+  Lock lock_;
+
   typedef base::hash_map<uint32, URLRequestRecord> URLRequestToRecordMap;
   typedef base::hash_map<uint32, ConnectJobRecord> ConnectJobToRecordMap;
   typedef base::hash_map<uint32, SocketRecord> SocketToRecordMap;