Multiple stubs can point to the same calling convention.

src/isolate.cc

Index: src/isolate.cc
diff --git a/src/isolate.cc b/src/isolate.cc
index 028da3d8fc86a62000087050955f817563a74372..5740b32497b7c3cc5456a58c3680ef225dec8f40 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -1920,6 +1920,8 @@ bool Isolate::Init(Deserializer* des) {
 
   deoptimizer_data_ = new DeoptimizerData(memory_allocator_);
 
+  CallDescriptors::InitializeForIsolate(this);
+
   const bool create_heap_objects = (des == NULL);
   if (create_heap_objects && !heap_.CreateHeapObjects()) {
     V8::FatalProcessOutOfMemory("heap object creation");
@@ -2030,8 +2032,6 @@ bool Isolate::Init(Deserializer* des) {
         kDeoptTableSerializeEntryCount - 1);
   }
 
-  CallDescriptors::InitializeForIsolate(this);
-
   if (!serializer_enabled()) {
     // Ensure that all stubs which need to be generated ahead of time, but
     // cannot be serialized into the snapshot have been generated.