Two simple profiler changes: 1) log sampling rate, 2) check current state before pausing & resuming.

src/log.h

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 202 matching lines @@
 
   // 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);
 
   // Logs all compiled functions found in the heap.
   static void LogCompiledFunctions();
 
  private:
 
+  // Profiler's sampling interval (in milliseconds).
+  static const int kSamplingIntervalMs = 1;
+
+  // Emits the profiler's first message.
+  static void ProfilerBeginEvent();
+
   // Emits the source code of a regexp. Used by regexp events.
   static void LogRegExpSource(Handle<JSRegExp> regexp);
 
   // Emits a profiler tick event. Used by the profiler thread.
   static void TickEvent(TickSample* sample, bool overflow);
 
   static void ApiEvent(const char* name, ...);
 
   // Logs a StringEvent regardless of whether FLAG_log is true.
   static void UncheckedStringEvent(const char* name, const char* value);
@@ skipping 45 matching lines @@
   void Trace(TickSample* sample);
  private:
 
   uintptr_t low_stack_bound_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_LOG_H_