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

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index a1e2e1671e42c0e7072e05fa194688400a41e296..c67193d2e3f5753449a0a80b27e27490cbd394d2 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -6439,5 +6439,34 @@ void Heap::CheckpointObjectStats() {
   MemCopy(object_sizes_last_time_, object_sizes_, sizeof(object_sizes_));
   ClearObjectStats();
 }
+
+
+const char* Heap::GetObjectTypeName(size_t index) {
+  if (index >= OBJECT_STATS_COUNT) return nullptr;
+
+  switch (static_cast<int>(index)) {
+#define COMPARE_AND_RETURN_NAME(name) \
+  case name:                          \
+    return #name;
+    INSTANCE_TYPE_LIST(COMPARE_AND_RETURN_NAME)
+#undef COMPARE_AND_RETURN_NAME
+#define COMPARE_AND_RETURN_NAME(name)         \
+  case FIRST_CODE_KIND_SUB_TYPE + Code::name: \
+    return "CODE_TYPE/CODE_KIND/" #name;
+    CODE_KIND_LIST(COMPARE_AND_RETURN_NAME)
+#undef COMPARE_AND_RETURN_NAME
+#define COMPARE_AND_RETURN_NAME(name)     \
+  case FIRST_FIXED_ARRAY_SUB_TYPE + name: \
+    return "FIXED_ARRAY_TYPE/" #name;
+    FIXED_ARRAY_SUB_INSTANCE_TYPE_LIST(COMPARE_AND_RETURN_NAME)
+#undef COMPARE_AND_RETURN_NAME
+#define COMPARE_AND_RETURN_NAME(name)                                          \
+  case FIRST_CODE_AGE_SUB_TYPE + Code::k##name##CodeAge - Code::kFirstCodeAge: \
+    return "CODE_TYPE/CODE_AGE/" #name;
+    CODE_AGE_LIST_COMPLETE(COMPARE_AND_RETURN_NAME)
+#undef COMPARE_AND_RETURN_NAME
+  }
+  return nullptr;
+}
 }
 }  // namespace v8::internal