Do not recompute unary_checks repeatedly. Add special (and quicker) way to check for method overrid…

runtime/vm/cha.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_CHA_H_
 #define VM_CHA_H_
 
 #include "vm/allocation.h"
 
 namespace dart {
 
+class Class;
 class Function;
 template <typename T> class ZoneGrowableArray;
 class String;
 
 class CHA : public AllStatic {
  public:
   // Returns true if the class given by its cid has subclasses.
   static bool HasSubclasses(intptr_t cid);
 
   // Returns an array containing the cids of the direct and indirect subclasses
   // of the class given by its cid.
   // Must not be called for kInstanceCid.
   static ZoneGrowableArray<intptr_t>* GetSubclassIdsOf(intptr_t cid);
 
   // Returns an array containing instance functions of the given name and
   // belonging to the classes given by their cids.
   // Cids must not contain kInstanceCid.
   static ZoneGrowableArray<Function*>* GetNamedInstanceFunctionsOf(
       const ZoneGrowableArray<intptr_t>& cids,
       const String& function_name);
 
   // Returns an array of functions overriding the given function.
   // Must not be called for a function of class Object.
   static ZoneGrowableArray<Function*>* GetOverridesOf(const Function& function);
+
+  // Returns true if any subclass of 'cls' contains the function.
+  static bool HasOverride(const Class& cls, const String& function_name);
 };
 
 }  // namespace dart
 
 #endif  // VM_CHA_H_