Update NetLog to be thread safe.

chrome/browser/net/chrome_net_log.h

Index: chrome/browser/net/chrome_net_log.h
===================================================================
--- chrome/browser/net/chrome_net_log.h	(revision 65207)
+++ chrome/browser/net/chrome_net_log.h	(working copy)
@@ -6,8 +6,10 @@
 #define CHROME_BROWSER_NET_CHROME_NET_LOG_H_
 #pragma once
 
+#include "base/atomicops.h"
 #include "base/observer_list.h"
 #include "base/scoped_ptr.h"
+#include "chrome/browser/browser_thread.h"
 #include "net/base/net_log.h"
 
 class LoadTimingObserver;
@@ -17,6 +19,10 @@
 // ChromeNetLog is an implementation of NetLog that dispatches network log
 // messages to a list of observers.
 //
+// All methods are threadsafe, with the exception that no ChromeNetLog or
+// ChromeNetLog::Observer functions may be called by an Observer's OnAddEntry()
+// method.
+//
 // By default, ChromeNetLog will attach the observer PassiveLogCollector which
 // will keep track of recent request information (which used when displaying
 // the about:net-internals page).
@@ -25,6 +31,28 @@
 //
 class ChromeNetLog : public net::NetLog {
  public:
+  // This structure encapsulates all of the parameters of an event,
+  // including an "order" field that identifies when it was captured relative
+  // to other events.
+  struct Entry {
+    Entry(uint32 order,
+          net::NetLog::EventType type,
+          const base::TimeTicks& time,
+          net::NetLog::Source source,
+          net::NetLog::EventPhase phase,
+          net::NetLog::EventParameters* params);
+    ~Entry();
+
+    uint32 order;
+    net::NetLog::EventType type;
+    base::TimeTicks time;
+    net::NetLog::Source source;
+    net::NetLog::EventPhase phase;
+    scoped_refptr<net::NetLog::EventParameters> params;
+  };
+
+  typedef std::vector<Entry> EntryList;
+
   // Interface for observing the events logged by the network stack.
   class Observer {
    public:
@@ -35,10 +63,16 @@
     //
     // Observers that need to see the full granularity of events can
     // specify LOG_ALL. However doing so will have performance consequences,
-    // and may cause PassiveLogCollector to use more memory than anticiapted.
+    // and may cause PassiveLogCollector to use more memory than anticipated.
+    //
+    // Observers will be called on the same thread an entry is added on,
+    // and are responsible for ensuring their own thread safety.
     explicit Observer(LogLevel log_level);
 
     virtual ~Observer() {}
+
+    // It is illegal for an Observer to call any ChromeNetLog or
+    // ChromeNetLog::Observer functions in response to a call to OnAddEntry.
     virtual void OnAddEntry(EventType type,
                             const base::TimeTicks& time,
                             const Source& source,
@@ -46,7 +80,9 @@
                             EventParameters* params) = 0;
     LogLevel log_level() const;
    protected:
-    void set_log_level(LogLevel log_level);
+    // |net_log| is the ChromeNetLog the Observer is currently observing,
+    // if any.
+    void set_log_level(LogLevel log_level, ChromeNetLog* net_log);

[eroman, 2010/11/16 17:51:14]

Please rename this to SetLogLevel(). (The hacker_notation() is only for raw
setters/getters).

    private:
     LogLevel log_level_;
     DISALLOW_COPY_AND_ASSIGN(Observer);
@@ -67,6 +103,13 @@
   void AddObserver(Observer* observer);
   void RemoveObserver(Observer* observer);
 
+  // Adds |observer| and writes all passively captured events to
+  // |passive_entries|. Guarantees that no events in |passive_entries| will be
+  // sent to |observer| and all future events that have yet been sent to the
+  // PassiveLogCollector will be sent to |observer|.
+  void AddObserverAndGetAllCapturedEvents(Observer* observer,
+                                          EntryList* passive_entries);
+
   PassiveLogCollector* passive_collector() {
     return passive_collector_.get();
   }
@@ -76,14 +119,20 @@
   }
 
  private:
-  uint32 next_id_;
+  // Called whenever an Observer is added or removed, or changes it log level.

[eroman, 2010/11/16 17:51:14]

change it log level --> changes its log level.

+  // Must have locked |lock_| prior to calling.

[eroman, 2010/11/16 17:51:14]

nit: "locked" --> acquired.

+  void UpdateLogLevel_();
+
+  Lock lock_;
+
+  base::subtle::Atomic32 last_id_;
+  base::subtle::Atomic32 log_level_;
+
   scoped_ptr<PassiveLogCollector> passive_collector_;
   scoped_ptr<LoadTimingObserver> load_timing_observer_;
   scoped_ptr<NetLogLogger> net_log_logger_;
 
-  // Note that this needs to be "mutable" so we can iterate over the observer
-  // list in GetLogLevel().
-  mutable ObserverList<Observer, true> observers_;
+  ObserverList<Observer, true> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeNetLog);
 };