AllocationSite objects weakly linked for traversal

src/assembler.h

Index: src/assembler.h
diff --git a/src/assembler.h b/src/assembler.h
index 95853e8e3a3b0ae099797f047f66e07e5ce0b09e..5cdddeba794f374c49a2b57cf45377803e2dd797 100644
--- a/src/assembler.h
+++ b/src/assembler.h
@@ -747,6 +747,9 @@ class ExternalReference BASE_EMBEDDED {
   // Static variable Heap::roots_array_start()
   static ExternalReference roots_array_start(Isolate* isolate);
 
+  // Static variable Heap::allocation_sites_list_address()
+  static ExternalReference allocation_sites_list_address(Isolate* isolate);
+
   // Static variable StackGuard::address_of_jslimit()
   static ExternalReference address_of_stack_limit(Isolate* isolate);