AllocationSite objects weakly linked for traversal

src/assembler.cc

Index: src/assembler.cc
diff --git a/src/assembler.cc b/src/assembler.cc
index 16a73a7f5076843920c7adebfb800dbc104be7eb..82c3c837075d931c7828d94e4001235ab63e933f 100644
--- a/src/assembler.cc
+++ b/src/assembler.cc
@@ -1125,6 +1125,12 @@ ExternalReference ExternalReference::roots_array_start(Isolate* isolate) {
 }
 
 
+ExternalReference ExternalReference::allocation_sites_list_address(
+    Isolate* isolate) {
+  return ExternalReference(isolate->heap()->allocation_sites_list_address());
+}
+
+
 ExternalReference ExternalReference::address_of_stack_limit(Isolate* isolate) {
   return ExternalReference(isolate->stack_guard()->address_of_jslimit());
 }