Recognize and optimize a.runtimeType == b.runtimeType pattern.

runtime/vm/isolate.h

Index: runtime/vm/isolate.h
diff --git a/runtime/vm/isolate.h b/runtime/vm/isolate.h
index 12dd5fa2f6fdcc37fd861a2de0c6adc4eb08164f..bf5f27121dec4f68432d77afcf82745a256d37f3 100644
--- a/runtime/vm/isolate.h
+++ b/runtime/vm/isolate.h
@@ -211,6 +211,9 @@ class Isolate : public BaseIsolate {
 
   ObjectStore* object_store() const { return object_store_; }
   void set_object_store(ObjectStore* value) { object_store_ = value; }
+  static intptr_t object_store_offset() {
+    return OFFSET_OF(Isolate, object_store_);
+  }
 
   ApiState* api_state() const { return api_state_; }
   void set_api_state(ApiState* value) { api_state_ = value; }