Convert String and List to abstract classes.

runtime/vm/object.h

Index: runtime/vm/object.h
diff --git a/runtime/vm/object.h b/runtime/vm/object.h
index 14a6222d8457a31ceba53c6b6fe927566609f8cd..987782c2429908d096694924b5e520130d2f828b 100644
--- a/runtime/vm/object.h
+++ b/runtime/vm/object.h
@@ -3094,14 +3094,14 @@ class AbstractType : public Instance {
   // Check if this type represents the 'num' type.
   bool IsNumberType() const;
 
-  // Check if this type represents the 'String' interface.
-  bool IsStringInterface() const;
+  // Check if this type represents the 'String' type.
+  bool IsStringType() const;
 
   // Check if this type represents the 'Function' type.
   bool IsFunctionType() const;
 
-  // Check if this type represents the 'List' interface.
-  bool IsListInterface() const;
+  // Check if this type represents the 'List' type.
+  bool IsListType() const;
 
   // Check if this type is an interface type.
   bool IsInterfaceType() const {
@@ -3218,14 +3218,14 @@ class Type : public AbstractType {
   // The 'num' interface type.
   static RawType* Number();
 
-  // The 'String' interface type.
-  static RawType* StringInterface();
+  // The 'String' type.
+  static RawType* StringType();
 
   // The 'Function' interface type.
   static RawType* Function();
 
-  // The 'List' interface type.
-  static RawType* ListInterface();
+  // The 'List' type.
+  static RawType* ListType();
 
   // The finalized type of the given non-parameterized class.
   static RawType* NewNonParameterizedType(const Class& type_class);