Fix a bug in instance canonicalization and add debug mode checks that we are not missing any fields.

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 3513 matching lines @@
 class Instance : public Object {
  public:
   virtual bool Equals(const Instance& other) const;
   // Returns Instance::null() if instance cannot be canonicalized.
   // Any non-canonical number of string will be canonicalized here.
   // An instance cannot be canonicalized if it still contains non-canonical
   // instances in its fields.
   // Returns error in error_str, pass NULL if an error cannot occur.
   virtual RawInstance* CheckAndCanonicalize(const char** error_str) const;
 
+  // Returns true if all fields are OK for canonicalization.
+  virtual bool CheckAndCanonicalizeFields(const char** error_str) const;
+
   RawObject* GetField(const Field& field) const {
     return *FieldAddr(field);
   }
 
   void SetField(const Field& field, const Object& value) const {
     StorePointer(FieldAddr(field), value.raw());
   }
 
   RawType* GetType() const;
 
@@ skipping 1433 matching lines @@
     return 0;
   }
 
   static intptr_t InstanceSize(intptr_t len) {
     // Ensure that variable length data is not adding to the object length.
     ASSERT(sizeof(RawArray) == (sizeof(RawInstance) + (2 * kWordSize)));
     ASSERT(0 <= len && len <= kMaxElements);
     return RoundedAllocationSize(sizeof(RawArray) + (len * kBytesPerElement));
   }
 
+  // Returns true if all elements are OK for canonicalization.
+  virtual bool CheckAndCanonicalizeFields(const char** error_str) const;
+
   // Make the array immutable to Dart code by switching the class pointer
   // to ImmutableArray.
   void MakeImmutable() const;
 
   static RawArray* New(intptr_t len, Heap::Space space = Heap::kNew);
 
   // Creates and returns a new array with 'new_length'. Copies all elements from
   // 'source' to the new array. 'new_length' must be greater than or equal to
   // 'source.Length()'. 'source' can be null.
   static RawArray* Grow(const Array& source,
@@ skipping 914 matching lines @@
 
 
 RawObject* MegamorphicCache::GetTargetFunction(const Array& array,
                                                intptr_t index) {
   return array.At((index * kEntryLength) + kTargetFunctionIndex);
 }
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_H_