Introduce internal Log class that handles writing log messages, enable logging to memory buffer.

src/log.h

Index: src/log.h
diff --git a/src/log.h b/src/log.h
index 44c1957697c7220942dce041ddba90d60cce8adf..a7c6604a178d2106e52325f326ec623a402870d6 100644
--- a/src/log.h
+++ b/src/log.h
@@ -103,10 +103,10 @@ class VMState BASE_EMBEDDED {
 
 class Logger {
  public:
-  // Opens the file for logging if the right flags are set.
+  // Acquires resources for logging if the right flags are set.
   static bool Setup();
 
-  // Closes file opened in Setup.
+  // Frees resources acquired in Setup.
   static void TearDown();
 
   // Enable the computation of a sliding window of states.
@@ -201,7 +201,7 @@ class Logger {
     return current_state_ ? current_state_->state() : OTHER;
   }
 
-  static bool is_enabled() { return logfile_ != NULL; }
+  static bool is_enabled();
 
   // Pause/Resume collection of profiling data.
   // When data collection is paused, Tick events are discarded until
@@ -210,6 +210,10 @@ class Logger {
   static void PauseProfiler();
   static void ResumeProfiler();
 
+  // If logging is performed into a memory buffer, allows to
+  // retrieve previously written messages. See v8.h.
+  static int GetLogLines(int from_pos, char* dest_buf, int max_size);
+
  private:
 
   // Emits the source code of a regexp. Used by regexp events.
@@ -223,17 +227,6 @@ class Logger {
   // Logs a StringEvent regardless of whether FLAG_log is true.
   static void UncheckedStringEvent(const char* name, const char* value);
 
-  // Size of buffer used for formatting log messages.
-  static const int kMessageBufferSize = 2048;
-
-  // Buffer used for formatting log messages. This is a singleton buffer and
-  // mutex_ should be acquired before using it.
-  static char* message_buffer_;
-
-  // When logging is active, logfile_ refers the file events are written to.
-  // mutex_ should be acquired before using logfile_.
-  static FILE* logfile_;
-
   // The sampler used by the profiler and the sliding state window.
   static Ticker* ticker_;
 
@@ -242,10 +235,6 @@ class Logger {
   // of samples.
   static Profiler* profiler_;
 
-  // mutex_ is a Mutex used for enforcing exclusive
-  // access to the formatting buffer and the log file.
-  static Mutex* mutex_;
-
   // A stack of VM states.
   static VMState* current_state_;
 
@@ -258,7 +247,6 @@ class Logger {
 
   // Internal implementation classes with access to
   // private members.
-  friend class LogMessageBuilder;
   friend class EventLog;
   friend class TimeLog;
   friend class Profiler;