Adding api to get last gc object statistics for chrome://tracing.

include/v8.h

 // Copyright 2012 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.
 
 /** \mainpage V8 API Reference Guide
  *
  * V8 is Google's open source JavaScript engine.
  *
  * This set of documents provides reference material generated from the
  * V8 header file, include/v8.h.
@@ skipping 4797 matching lines @@
   const char* space_name_;
   size_t space_size_;
   size_t space_used_size_;
   size_t space_available_size_;
   size_t physical_space_size_;
 
   friend class Isolate;
 };
 
 
+class V8_EXPORT HeapObjectStatistics {
+ public:
+  HeapObjectStatistics();
+  const char* object_type() { return object_type_; }

[Primiano Tucci (use gerrit), 2015/05/07 16:54:15]

I wonder here if the right thing to do is concatenating types with slashes (e.g.
"CODE/CODE_AGE/IsExecuted"), or if we should expose them separately at an API
level, something like
const char* object_type();
const char* object_subtype();  // This will be "" for most of the entries, %
code_age, kind and fixed_array.

Ulan, WDYT?

+  size_t object_count() { return object_count_; }
+  size_t object_size() { return object_size_; }
+
+ private:
+  const char* object_type_;
+  size_t object_count_;
+  size_t object_size_;
+
+  friend class Isolate;
+};
+
+
 class RetainedObjectInfo;
 
 
 /**
  * FunctionEntryHook is the type of the profile entry hook called at entry to
  * any generated function when function-level profiling is enabled.
  *
  * \param function the address of the function that's being entered.
  * \param return_addr_location points to a location on stack where the machine
  *    return address resides. This can be used to identify the caller of
@@ skipping 368 matching lines @@
    * \param space_statistics The HeapSpaceStatistics object to fill in
    *   statistics.
    * \param index The index of the space to get statistics from, which ranges
    *   from 0 to NumberOfHeapSpaces() - 1.
    * \returns true on success.
    */
   bool GetHeapSpaceStatistics(HeapSpaceStatistics* space_statistics,
                               size_t index);
 
   /**
+   * Returns the number of types of objects tracked in the heap at GC.
+   */
+  size_t NumberOfTrackedHeapObjectTypes();
+
+  /**
+   * Get statistics about objects in the heap.
+   *
+   * \param object_statistics The HeapObjectStatistics object to fill in
+   *   statistics of objects of given type, which were live in the previous GC.
+   * \param type_index The index of the type of object to fill details about,
+   *   which ranges from 0 to NumberOfHeapObjectsTypes() - 1.
+   * \returns true on success.
+   */
+  bool GetHeapObjectStatisticsAtLastGC(HeapObjectStatistics* object_statistics,
+                                       size_t type_index);
+
+  /**
    * Get a call stack sample from the isolate.
    * \param state Execution state.
    * \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.
    * \note GetStackSample should only be called when the JS thread is paused or
    *       interrupted. Otherwise the behavior is undefined.
@@ skipping 2805 matching lines @@
  */
 
 
 }  // namespace v8
 
 
 #undef TYPE_CHECK
 
 
 #endif  // V8_H_