Initial GetSample implementation.

include/v8.h

Index: include/v8.h
diff --git a/include/v8.h b/include/v8.h
index e3cd10fa8d690cca9ddf4ed5b8fdbc4a1f366f67..9b46a742dd1a7553c06a339e6688087684b285a6 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -1322,6 +1322,41 @@ class V8_EXPORT StackFrame {
 
 
 /**
+ * Isolate::GetSample collects the current JS execution state as a sample.
+ * A collected sample contains program counter values.
+ *
+ * Example: Printing out the stack frames' addresses, from top to bottom.
+ *
+ * Isolate* isolate = Isolate::Current();
+ * Sample sample;
+ * isolate->GetSample(&sample);
+ * const void* const* i;
+ * for (i = sample.begin(); i != sample.end(); ++i) {
+ *   printf("%p\n", *i);
+ * }
+ */
+class V8_EXPORT Sample {
+ public:
+  enum { kMaxSize = 255u };
+
+  Sample() : size_(0) {}
+  template <class InputIterator>
+  Sample(InputIterator first, InputIterator last)
+      : size_(0) {
+    for (; first != last && size_ < kMaxSize; ++first) data_[size_++] = *first;
+  }
+
+  typedef const void* const* const_iterator;
+  const_iterator begin() const { return &data_[0]; }
+  const_iterator end() const { return &data_[size_]; }
+  size_t size() const { return size_; }
+
+ private:
+  const void* data_[kMaxSize];
+  size_t size_;
+};
+
+/**
  * A JSON Parser.
  */
 class V8_EXPORT JSON {
@@ -4319,6 +4354,11 @@ class V8_EXPORT Isolate {
   void GetHeapStatistics(HeapStatistics* heap_statistics);
 
   /**
+   * Get a sample from the isolate.
+   */
+  void GetSample(Sample* sample);

[yurys, 2014/09/09 14:35:20]

This is not what the document proposed. The idea was to expose an API for
collecting current v8 stack trace on a paused thread. It is the embedder who
should be responsible for pausing the thread (using SIGPROF or SuspendThread)
and calling GetSample. Introducing such API would allow us to move profiler
implementation out of V8 into e.g. Blink. With GetSample introduced in this CL
we will have to keep all the platform-specific profiler code in v8.

[jochen (gone - plz use gerrit), 2014/09/10 07:39:20]

Agreed.

We'll soon delete threads from v8 and instead solely rely on embedder threads,
then this won't work anymore anyways

[gholap, 2014/09/17 02:35:06]

Acknowledged.

+
+  /**
    * Adjusts the amount of registered external memory. Used to give V8 an
    * indication of the amount of externally allocated memory that is kept alive
    * by JavaScript objects. V8 uses this to decide when to perform global