Introduce a way to grab heap stats.

include/v8-profiler.h

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 // modification, are permitted provided that the following conditions are
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@@ skipping 400 matching lines @@
   /**
    * Takes a heap snapshot and returns it. Title may be an empty string.
    * See HeapSnapshot::Type for types description.
    */
   static const HeapSnapshot* TakeSnapshot(
       Handle<String> title,
       HeapSnapshot::Type type = HeapSnapshot::kFull,
       ActivityControl* control = NULL);
 
   /**
+   * This method gives us an update of the heap state.

[mnaganov (inactive), 2012/04/12 13:32:26]

Comments look a bit weird. How about putting StartHeapObjectsTracking first, and
annotating it something like this:

"Starts tracking of heap objects population statistics. After calling this
method, all heap objects relocations done by the garbage collector are being
registered."

Then, for PushHeapObjectsStats we can write something like:

"Adds a new time interval entry to the aggregated statistics array. The time
interval entry contains information on the current heap objects population size.
The method also updates aggregated statistics and reports updates for all
previous time intervals via the OutputStream object. Updates on each time
interval are provided as pairs of time interval index and updated heap objects
count.

StartHeapObjectsTracking must be called before the first call to this method."

And for StopHeapObjectsTracking:

"Stops tracking of heap objects population statistics, cleans up all collected
data. StartHeapObjectsTracking must be called again prior to calling
PushHeapObjectsStats next time."

+   * It appends a new time interval to an aggegated stats array,
+   * traverse the heap and: assign ids to new objects, remove ids of collected
+   * objects, count of alive objects for the each time interval and if the stats
+   * for a time interval were changed, report the new stats to the caller via
+   * OutputStream object.
+   */
+  static void PushHeapObjectsStats(OutputStream* stream);

[mnaganov (inactive), 2012/04/12 13:32:26]

nit: add a blank line before the comment

+  /**
+   * At GC phase objects can be moved and we want to track these movements.
+   * in the other case we will count moved objects as new.
+   */
+  static void StartHeapObjectsTracking();

[mnaganov (inactive), 2012/04/12 13:32:26]

nit: add a blank line before the comment

+  /**
+   * Stop objects movements tracking and clean the list of time intervals.
+   */
+  static void StopHeapObjectsTracking();
+
+  /**
    * Deletes all snapshots taken. All previously returned pointers to
    * snapshots and their contents become invalid after this call.
    */
   static void DeleteAllSnapshots();
 
   /** Binds a callback to embedder's class ID. */
   static void DefineWrapperClass(
       uint16_t class_id,
       WrapperInfoCallback callback);
 
@@ skipping 83 matching lines @@
 };
 
 
 }  // namespace v8
 
 
 #undef V8EXPORT
 
 
 #endif  // V8_V8_PROFILER_H_