Add field nested_sites to AllocationSite.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index f45dd4c0f70f3e33b4efbf98a3c37db27efe19d8..592c37fea7f5938035ee143b309c4b8b98dae411 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -8953,6 +8953,24 @@ Handle<String> SeqString::Truncate(Handle<SeqString> string, int new_length) {
 }
 
 
+AllocationSite* AllocationSite::GetLastNestedSite() {
+  AllocationSite* current_site = this;
+  while (current_site->nested_sites() != Smi::FromInt(0)) {
+    current_site = AllocationSite::cast(current_site->nested_sites());
+  }
+  return current_site == this ? NULL : current_site;
+}
+
+
+void AllocationSite::AppendNestedSite(AllocationSite* nested_site) {
+  AllocationSite* last_nested_site = GetLastNestedSite();
+  AllocationSite* append_to = last_nested_site == NULL
+      ? this
+      : last_nested_site;
+  append_to->set_nested_sites(nested_site);
+}
+
+
 AllocationMemento* AllocationMemento::FindForJSObject(JSObject* object) {
   // Currently, AllocationMemento objects are only allocated immediately
   // after JSArrays in NewSpace, and detecting whether a JSArray has one