Implement resource-saving mode of Profiler.

src/platform.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 500 matching lines @@
   // program counter.
   virtual void Tick(TickSample* sample) = 0;
 
   // Start and stop sampler.
   void Start();
   void Stop();
 
   // Is the sampler used for profiling.
   inline bool IsProfiling() { return profiling_; }
 
+  // Whether the sampler is running (that is, consumes resources).
+  inline bool IsActive() { return active_; }
+
   class PlatformData;
- protected:
-  inline bool IsActive() { return active_; }
 
  private:
   int interval_;
   bool profiling_;
   bool active_;
   PlatformData* data_;  // Platform specific data.
   DISALLOW_IMPLICIT_CONSTRUCTORS(Sampler);
 };
 
 #endif  // ENABLE_LOGGING_AND_PROFILING
 
 } }  // namespace v8::internal
 
 #endif  // V8_PLATFORM_H_