Refactor net::NetLog to provide implementation of observer pattern, not just the interface.

net/base/net_log.h

Index: net/base/net_log.h
diff --git a/net/base/net_log.h b/net/base/net_log.h
index 8ae33e94b745e050eae956b3a1c0a5aac452b133..863080f814faa0b54d4ed2b5e20aee2729eeacc4 100644
--- a/net/base/net_log.h
+++ b/net/base/net_log.h
@@ -10,6 +10,7 @@
 #include "base/basictypes.h"
 #include "base/callback_forward.h"
 #include "base/compiler_specific.h"
+#include "base/observer_list.h"
 #include "base/string16.h"
 #include "base/time.h"
 #include "net/base/net_export.h"
@@ -198,8 +199,8 @@ class NET_EXPORT NetLog {
     DISALLOW_COPY_AND_ASSIGN(ThreadSafeObserver);
   };
 
-  NetLog() {}
-  virtual ~NetLog() {}
+  explicit NetLog(LogLevel base_log_level = LOG_NONE);

[mmenke, 2013/05/30 18:18:59]

The Google style guide comes out pretty strongly against default values for
arguments.  I suggest just a SetBaseLogLevel function, which calls into
UpdateLogLevel().

[kouhei (in TOK), 2013/05/31 06:30:03]

Done.

+  virtual ~NetLog();
 
   // Emits a global event to the log stream, with its own unique source ID.
   void AddGlobalEntry(EventType type);
@@ -208,11 +209,11 @@ class NET_EXPORT NetLog {
 
   // Returns a unique ID which can be used as a source ID.  All returned IDs
   // will be unique and greater than 0.
-  virtual uint32 NextID() = 0;
+  uint32 NextID();
 
   // Returns the logging level for this NetLog. This is used to avoid computing
   // and saving expensive log entries.
-  virtual LogLevel GetLogLevel() const = 0;
+  LogLevel GetLogLevel() const;
 
   // Adds an observer and sets its log level.  The observer must not be
   // watching any NetLog, including this one, when this is called.
@@ -224,21 +225,19 @@ class NET_EXPORT NetLog {
   //
   // NetLog implementations must call NetLog::OnAddObserver to update the
   // observer's internal state.
-  virtual void AddThreadSafeObserver(ThreadSafeObserver* observer,
-                                     LogLevel log_level) = 0;
+  void AddThreadSafeObserver(ThreadSafeObserver* observer, LogLevel log_level);
 
   // Sets the log level of |observer| to |log_level|.  |observer| must be
   // watching |this|.  NetLog implementations must call
   // NetLog::OnSetObserverLogLevel to update the observer's internal state.
-  virtual void SetObserverLogLevel(ThreadSafeObserver* observer,
-                                   LogLevel log_level) = 0;
+  void SetObserverLogLevel(ThreadSafeObserver* observer, LogLevel log_level);
 
   // Removes an observer.  NetLog implementations must call
   // NetLog::OnAddObserver to update the observer's internal state.
   //
   // For thread safety reasons, it is recommended that this not be called in
   // an object's destructor.
-  virtual void RemoveThreadSafeObserver(ThreadSafeObserver* observer) = 0;
+  void RemoveThreadSafeObserver(ThreadSafeObserver* observer);
 
   // Converts a time to the string format that the NetLog uses to represent
   // times.  Strings are used since integers may overflow.
@@ -295,7 +294,7 @@ class NET_EXPORT NetLog {
  protected:
   // Child classes should respond to the new entry here.  This includes
   // creating the Entry object and alerting their observers.
-  virtual void OnAddEntry(const Entry& entry) = 0;
+  void OnAddEntry(const Entry& entry);
 
   // Subclasses must call these in the corresponding functions to set an
   // observer's |net_log_| and |log_level_| values.
@@ -312,6 +311,26 @@ class NET_EXPORT NetLog {
                 EventPhase phase,
                 const NetLog::ParametersCallback* parameters_callback);
 
+  // Called whenever an observer is added or removed, or has its log level
+  // changed.  Must have acquired |lock_| prior to calling.
+  void UpdateLogLevel();
+
+  // |lock_| protects access to |observers_|.
+  base::Lock lock_;

[mmenke, 2013/05/30 18:18:59]

Need a header for this.

[kouhei (in TOK), 2013/05/31 06:30:03]

Done.

+
+  // Last assigned source ID.  Incremented to get the next one.
+  base::subtle::Atomic32 last_id_;

[mmenke, 2013/05/30 18:18:59]

Need a header for this.

[kouhei (in TOK), 2013/05/31 06:30:03]

Done.

+
+  // The lowest allowed log level, regardless of any Observers.
+  // Normally defaults to LOG_NONE, but can be changed with command line flags.
+  const LogLevel base_log_level_;
+
+  // The current log level.
+  base::subtle::Atomic32 effective_log_level_;
+
+  // |lock_| must be acquired whenever reading or writing to this.
+  ObserverList<ThreadSafeObserver, true> observers_;
+
   DISALLOW_COPY_AND_ASSIGN(NetLog);
 };