Remove isolate pointer from context objects.

runtime/vm/raw_object_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/object.h"
 #include "vm/object_store.h"
 #include "vm/snapshot.h"
 #include "vm/stub_code.h"
 #include "vm/symbols.h"
 #include "vm/visitor.h"
@@ skipping 1347 matching lines @@
   if (kind == Snapshot::kFull) {
     context = reader->NewContext(num_vars);
   } else {
     context = Context::New(num_vars, HEAP_SPACE(kind));
   }
   reader->AddBackRef(object_id, &context, kIsDeserialized);
 
   // Set the object tags.
   context.set_tags(tags);
 
-  // Set the isolate implicitly.
-  context.set_isolate(reader->isolate());
-
   // Set all the object fields.
   // TODO(5411462): Need to assert No GC can happen here, even though
   // allocations may happen.
   intptr_t num_flds = (context.raw()->to(num_vars) - context.raw()->from());
   for (intptr_t i = 0; i <= num_flds; i++) {
     (*reader->PassiveObjectHandle()) = reader->ReadObjectRef();
     context.StorePointer((context.raw()->from() + i),
                          reader->PassiveObjectHandle()->raw());
   }
 
@@ skipping 1504 matching lines @@
     // We do not allow objects with native fields in an isolate message.
     writer->SetWriteException(Exceptions::kArgument,
                               "Illegal argument in isolate message"
                               " : (object is a UserTag)");
   } else {
     UNREACHABLE();
   }
 }
 
 }  // namespace dart