Get rid of UnsafeCurrent in Sampler

src/profiler/sampler.h

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_PROFILER_SAMPLER_H_
 #define V8_PROFILER_SAMPLER_H_
 
 #include "include/v8.h"
 
 #include "src/base/atomicops.h"
@@ skipping 74 matching lines @@
   bool IsProfiling() const {
     return base::NoBarrier_Load(&profiling_) > 0 &&
         !base::NoBarrier_Load(&has_processing_thread_);
   }
   void IncreaseProfilingDepth();
   void DecreaseProfilingDepth();
 
   // Whether the sampler is running (that is, consumes resources).
   bool IsActive() const { return base::NoBarrier_Load(&active_); }
 
+  // A sampler can be registered when Start() doesn't get called,
+  // since CpuProfiler won't start the sampler but need to collect samples.
+  bool IsRegistered() const { return base::NoBarrier_Load(&registered_); }
+
   void DoSample();
   // If true next sample must be initiated on the profiler event processor
   // thread right after latest sample is processed.
   void SetHasProcessingThread(bool value) {
     base::NoBarrier_Store(&has_processing_thread_, value);
   }
 
   // Used in tests to make sure that stack sampling is performed.
   unsigned js_sample_count() const { return js_sample_count_; }
   unsigned external_sample_count() const { return external_sample_count_; }
   void StartCountingSamples() {
     js_sample_count_ = 0;
     external_sample_count_ = 0;
     is_counting_samples_ = true;
   }
 
   class PlatformData;
   PlatformData* platform_data() const { return data_; }
 
  protected:
   // This method is called for each sampling period with the current
   // program counter.
   virtual void Tick(TickSample* sample) = 0;
 
  private:
   void SetActive(bool value) { base::NoBarrier_Store(&active_, value); }
 
+  void SetRegistered(bool value) { base::NoBarrier_Store(&registered_, value); }
+
   Isolate* isolate_;
   const int interval_;
   base::Atomic32 profiling_;
   base::Atomic32 has_processing_thread_;
   base::Atomic32 active_;
+  base::Atomic32 registered_;
   PlatformData* data_;  // Platform specific data.
   // Counts stack samples taken in various VM states.
   bool is_counting_samples_;
   unsigned js_sample_count_;
   unsigned external_sample_count_;
   DISALLOW_IMPLICIT_CONSTRUCTORS(Sampler);
 };
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PROFILER_SAMPLER_H_