Add --dump-megamorphic-stats. Lower megamorphic cache load factor to 50%.

runtime/vm/object.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_OBJECT_H_
 #define VM_OBJECT_H_
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/utils.h"
@@ skipping 5014 matching lines @@
   void EnsureCapacity() const;
 
   void Insert(const Smi& class_id, const Function& target) const;
 
   static intptr_t InstanceSize() {
     return RoundedAllocationSize(sizeof(RawMegamorphicCache));
   }
 
  private:
   friend class Class;
+  friend class MegamorphicCacheTable;
 
   static RawMegamorphicCache* New();
 
   void set_target_name(const String& value) const;
   void set_arguments_descriptor(const Array& value) const;
 
   enum {
     kClassIdIndex,
     kTargetFunctionIndex,
     kEntryLength,
@@ skipping 3665 matching lines @@
 
 inline void TypeArguments::SetHash(intptr_t value) const {
   // This is only safe because we create a new Smi, which does not cause
   // heap allocation.
   StoreSmi(&raw_ptr()->hash_, Smi::New(value));
 }
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_H_