When canonicalize instances check if all fields are canonical. If a field is a non-canonical number…

runtime/vm/snapshot.cc

 // 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.
 
 #include "vm/snapshot.h"
 
 #include "platform/assert.h"
 #include "vm/bigint_operations.h"
 #include "vm/bootstrap.h"
 #include "vm/class_finalizer.h"
@@ skipping 775 matching lines @@
     }
     intptr_t offset = Object::InstanceSize();
     while (offset < instance_size) {
       obj_ = ReadObjectRef();
       result->SetFieldAtOffset(offset, obj_);
       offset += kWordSize;
     }
     if (kind_ == Snapshot::kFull) {
       result->SetCreatedFromSnapshot();
     } else if (result->IsCanonical()) {
-      *result = result->Canonicalize();
+      *result = result->CheckAndCanonicalize(NULL);
+      ASSERT(!result->IsNull());
     }
     return result->raw();
   }
   ASSERT((class_header & kSmiTagMask) != kSmiTag);
   cls_ = LookupInternalClass(class_header);
   ASSERT(!cls_.IsNull());
   switch (cls_.id()) {
 #define SNAPSHOT_READ(clazz)                                                   \
     case clazz::kClassId: {                                                    \
       obj_ = clazz::ReadFrom(this, object_id, tags, kind_);                    \
@@ skipping 656 matching lines @@
     UnmarkAll();
     isolate->set_long_jump_base(base);
   } else {
     isolate->set_long_jump_base(base);
     ThrowException(exception_type(), exception_msg());
   }
 }
 
 
 }  // namespace dart