ExtendStorageStub added, it is aimed for extending objects backing store when it runs out of space.

src/arm64/interface-descriptors-arm64.cc

Index: src/arm64/interface-descriptors-arm64.cc
diff --git a/src/arm64/interface-descriptors-arm64.cc b/src/arm64/interface-descriptors-arm64.cc
index 690c8c28eeb83f16fede90bcae48612b2fa97214..f216e30786def75a5159f039d98e266a258f163e 100644
--- a/src/arm64/interface-descriptors-arm64.cc
+++ b/src/arm64/interface-descriptors-arm64.cc
@@ -29,6 +29,9 @@ const Register StoreDescriptor::NameRegister() { return x2; }
 const Register StoreDescriptor::ValueRegister() { return x0; }
 
 
+const Register ExtendStorageDescriptor::MapRegister() { return x3; }
+
+
 const Register ElementTransitionAndStoreDescriptor::MapRegister() { return x3; }