[api,profiler] Introduce GetRetainerInfos callback for profiling

include/v8-profiler.h

Index: include/v8-profiler.h
diff --git a/include/v8-profiler.h b/include/v8-profiler.h
index 74c0613946d5131910a42a46a84a8c83b8f32c96..b0a81f2b0b9c0ce5e7f9f3d63327764ac9ae3ff7 100644
--- a/include/v8-profiler.h
+++ b/include/v8-profiler.h
@@ -5,6 +5,7 @@
 #ifndef V8_V8_PROFILER_H_
 #define V8_V8_PROFILER_H_
 
+#include <unordered_set>
 #include <vector>
 #include "v8.h"  // NOLINT(build/include)
 
@@ -630,6 +631,24 @@ class V8_EXPORT HeapProfiler {
     kSamplingForceGC = 1 << 0,
   };
 
+  typedef std::unordered_set<const v8::PersistentBase<v8::Value>*>
+      RetainerChildren;
+  typedef std::vector<std::pair<v8::RetainedObjectInfo*, RetainerChildren>>
+      RetainerGroups;
+  typedef std::vector<std::pair<const v8::PersistentBase<v8::Value>*,
+                                const v8::PersistentBase<v8::Value>*>>
+      RetainerEdges;
+
+  struct RetainerInfos {
+    RetainerGroups groups;
+    RetainerEdges edges;
+  };
+
+  /**
+   * Callback function invoked to retrieve all RetainerInfos from the embedder.
+   */
+  typedef RetainerInfos (*GetRetainerInfosCallback)(v8::Isolate* isolate);
+
   /**
    * Callback function invoked for obtaining RetainedObjectInfo for
    * the given JavaScript wrapper object. It is prohibited to enter V8
@@ -782,6 +801,8 @@ class V8_EXPORT HeapProfiler {
       uint16_t class_id,
       WrapperInfoCallback callback);
 
+  void SetGetRetainerInfosCallback(GetRetainerInfosCallback callback);
+
   /**
    * Default value of persistent handle class ID. Must not be used to
    * define a class. Can be used to reset a class of a persistent