Move SimulatorHelper into V8 out of profiler clients.

include/v8-profiler.h

Index: include/v8-profiler.h
diff --git a/include/v8-profiler.h b/include/v8-profiler.h
index 29d3c84a740b03a87a72de28b38f93be3a044779..9b9d8fd3de3aa652dbcfedfc863df6793d01c0c6 100644
--- a/include/v8-profiler.h
+++ b/include/v8-profiler.h
@@ -60,12 +60,50 @@ struct TickSample {
         frames_count(0),
         has_external_callback(false),
         update_stats(true) {}
+
+  /**
+   * Initialize a tick sample from the isolate.
+   * \param isolate The currect isolate.
+   * \param state Execution state.
+   * \param updated_state When running on simulator, this will be set to
+                          the real register state used for sampling.
+   * \param record_c_entry_frame Include or skip the runtime function.
+   * \param update_stats Whether update the sample to the aggregated stats.
+   * \param use_first_state Force V8 to use the first register state to
+                            collect sample, default value is false, unless
+                            the first register state is absolutely correct,
+                            otherwise don't use it.
+   */
   void Init(Isolate* isolate, const v8::RegisterState& state,
-            RecordCEntryFrame record_c_entry_frame, bool update_stats);
+            RegisterState& updated_state,

[alph, 2016/07/28 23:57:06]

Hmm. Is it an output parameter? Where is it used?

+            RecordCEntryFrame record_c_entry_frame, bool update_stats,
+            bool use_first_state = false);

[alph, 2016/07/28 23:57:06]

The name looks a bit awkward. Not sure about a better name though. :-/

+  /**
+   * Get a call stack sample from the isolate.
+   * \param isolate The currect isolate.
+   * \param state Execution state.
+   * \param updated_state When running on simulator, this will be set to
+                          the real register state used for sampling.
+   * \param record_c_entry_frame Include or skip the runtime function.
+   * \param frames Caller allocated buffer to store stack frames.
+   * \param frames_limit Maximum number of frames to capture. The buffer must
+   *                     be large enough to hold the number of frames.
+   * \param sample_info The sample info is filled up by the function
+   *                    provides number of actual captured stack frames and
+   *                    the current VM state.
+   * \param use_first_state Force V8 to use the first register state to
+                            collect sample, default value is false, unless
+                            the first register state is absolutely correct,
+                            otherwise don't use it.
+   * \note GetStackSample should only be called when the JS thread is paused or
+   *       interrupted. Otherwise the behavior is undefined.
+   */
   static bool GetStackSample(Isolate* isolate, const v8::RegisterState& state,
+                             RegisterState& updated_state,
                              RecordCEntryFrame record_c_entry_frame,
                              void** frames, size_t frames_limit,
-                             v8::SampleInfo* sample_info);
+                             v8::SampleInfo* sample_info,
+                             bool use_first_state = false);
   StateTag state;  // The state of the VM.
   void* pc;        // Instruction pointer.
   union {