Convert double interface into abstract class

runtime/vm/object_store.h

Index: runtime/vm/object_store.h
===================================================================
--- runtime/vm/object_store.h	(revision 11396)
+++ runtime/vm/object_store.h	(working copy)
@@ -79,11 +79,6 @@
   void set_smi_type(const Type& value) { smi_type_ = value.raw();
   }
 
-  RawType* double_interface() const { return double_interface_; }
-  void set_double_interface(const Type& value) {
-    double_interface_ = value.raw();
-  }
-
   RawClass* double_class() const { return double_class_; }
   void set_double_class(const Class& value) { double_class_ = value.raw(); }
 
@@ -482,7 +477,6 @@
   RawClass* mint_class_;
   RawType* mint_type_;
   RawClass* bigint_class_;
-  RawType* double_interface_;
   RawClass* double_class_;
   RawType* double_type_;
   RawType* string_interface_;