Shrink some fields and add some bounds checks.

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 4710 matching lines @@
   friend class TypedDataView;
 };
 
 
 class LibraryPrefix : public Instance {
  public:
   RawString* name() const { return raw_ptr()->name_; }
   virtual RawString* DictionaryName() const { return name(); }
 
   RawArray* imports() const { return raw_ptr()->imports_; }
-  int32_t num_imports() const { return raw_ptr()->num_imports_; }
+  intptr_t num_imports() const { return raw_ptr()->num_imports_; }
   RawLibrary* importer() const { return raw_ptr()->importer_; }
 
   RawInstance* LoadError() const;
 
   bool ContainsLibrary(const Library& library) const;
   RawLibrary* GetLibrary(int index) const;
   void AddImport(const Namespace& import) const;
   RawObject* LookupObject(const String& name) const;
   RawClass* LookupClass(const String& class_name) const;
 
@@ skipping 3112 matching lines @@
 
 
 RawObject* MegamorphicCache::GetTargetFunction(const Array& array,
                                                intptr_t index) {
   return array.At((index * kEntryLength) + kTargetFunctionIndex);
 }
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_H_