VM: Use read-only handle Object::dynamic_type() where possible.

runtime/vm/flow_graph_optimizer.cc

 // Copyright (c) 2013, 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/flow_graph_optimizer.h"
 
 #include "vm/bit_vector.h"
 #include "vm/cha.h"
 #include "vm/compiler.h"
 #include "vm/cpu.h"
@@ skipping 1708 matching lines @@
                                        call->deopt_id()),
                                    call->env(),
                                    FlowGraph::kEffect);
 
   if (array_cid == kGrowableObjectArrayCid) {
     // Insert data elements load.
     LoadFieldInstr* elements =
         new(Z) LoadFieldInstr(
             new(Z) Value(*array),
             GrowableObjectArray::data_offset(),
-            Type::ZoneHandle(Z, Type::DynamicType()),
+            Object::dynamic_type(),
             call->token_pos());
     elements->set_result_cid(kArrayCid);
     *cursor = flow_graph()->AppendTo(*cursor,
                                      elements,
                                      NULL,
                                      FlowGraph::kValue);
     // Load from the data from backing store which is a fixed-length array.
     *array = elements;
     array_cid = kArrayCid;
   } else if (RawObject::IsExternalTypedDataClassId(array_cid)) {
@@ skipping 7113 matching lines @@
 
   // Insert materializations at environment uses.
   for (intptr_t i = 0; i < exits_collector_.exits().length(); i++) {
     CreateMaterializationAt(
         exits_collector_.exits()[i], alloc, *slots);
   }
 }
 
 
 }  // namespace dart