Initial GetSample implementation.

src/sampler.h

Index: src/sampler.h
diff --git a/src/sampler.h b/src/sampler.h
index c3dce4ed7c2fec7e353cb06d1641f63e82092a84..1a6c358ae9add0bfd0eb6a6284ab8196d5a3ef74 100644
--- a/src/sampler.h
+++ b/src/sampler.h
@@ -32,23 +32,27 @@ struct RegisterState {
 struct TickSample {
   TickSample()
       : state(OTHER),
+        frames_count(0),
         pc(NULL),
         external_callback(NULL),
-        frames_count(0),
         has_external_callback(false),
         top_frame_type(StackFrame::NONE) {}
-  void Init(Isolate* isolate, const RegisterState& state);
-  StateTag state;  // The state of the VM.
+  static const unsigned kMaxFramesCountLog2 = 8;
+  static const unsigned kMaxFramesCount = (1 << kMaxFramesCountLog2) - 1;
+
+  StateTag state;                               // The state of the VM.
+  Address stack[kMaxFramesCount];               // Call stack.
+  unsigned frames_count : kMaxFramesCountLog2;  // Number of captured frames.
+
+  void Init(Isolate* isolate,
+            const RegisterState& state,
+            unsigned max_frame_count = kMaxFramesCount);
   Address pc;      // Instruction pointer.
   union {
     Address tos;   // Top stack value (*sp).
     Address external_callback;
   };
-  static const unsigned kMaxFramesCountLog2 = 8;
-  static const unsigned kMaxFramesCount = (1 << kMaxFramesCountLog2) - 1;
-  Address stack[kMaxFramesCount];  // Call stack.
   base::TimeTicks timestamp;
-  unsigned frames_count : kMaxFramesCountLog2;  // Number of captured frames.
   bool has_external_callback : 1;
   StackFrame::Type top_frame_type : 4;
 };
@@ -85,6 +89,7 @@ class Sampler {
   bool IsActive() const { return base::NoBarrier_Load(&active_); }
 
   void DoSample();
+  void GetSample(TickSample* sample, unsigned max_frame_count);
   // If true next sample must be initiated on the profiler event processor
   // thread right after latest sample is processed.
   void SetHasProcessingThread(bool value) {
@@ -120,6 +125,8 @@ class Sampler {
   bool is_counting_samples_;
   // Counts stack samples taken in JS VM state.
   unsigned js_and_external_sample_count_;
+  void CaptureRegisterState_();
+  void CaptureRegisterState_(RegisterState* state, bool* captured_successfully);
   DISALLOW_IMPLICIT_CONSTRUCTORS(Sampler);
 };