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

runtime/vm/flow_graph_compiler_arm64.cc

 // Copyright (c) 2014, 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/globals.h"  // Needed here to get TARGET_ARCH_ARM64.
 #if defined(TARGET_ARCH_ARM64)
 
 #include "vm/flow_graph_compiler.h"
 
 #include "vm/ast_printer.h"
@@ skipping 434 matching lines @@
     // Load instantiator (or null) and instantiator type arguments on stack.
     __ ldr(R1, Address(SP));  // Get instantiator type arguments.
     // R1: instantiator type arguments.
     // Check if type arguments are null, i.e. equivalent to vector of dynamic.
     __ CompareObject(R1, Object::null_object());
     __ b(is_instance_lbl, EQ);
     __ LoadFieldFromOffset(
         R2, R1, TypeArguments::type_at_offset(type_param.index()));
     // R2: concrete type of type.
     // Check if type argument is dynamic.
-    __ CompareObject(R2, Type::ZoneHandle(zone(), Type::DynamicType()));
+    __ CompareObject(R2, Object::dynamic_type());
     __ b(is_instance_lbl, EQ);
     __ CompareObject(R2, Type::ZoneHandle(zone(), Type::ObjectType()));
     __ b(is_instance_lbl, EQ);
 
     // For Smi check quickly against int and num interfaces.
     Label not_smi;
     __ tsti(R0, Immediate(kSmiTagMask));  // Value is Smi?
     __ b(&not_smi, NE);
     __ CompareObject(R2, Type::ZoneHandle(zone(), Type::IntType()));
     __ b(is_instance_lbl, EQ);
@@ skipping 1391 matching lines @@
 void ParallelMoveResolver::RestoreFpuScratch(FpuRegister reg) {
   __ PopDouble(reg);
 }
 
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM64