Use Object::null_object() instead of Object::ZoneHandle() when a null object

runtime/vm/stub_code_mips_test.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/globals.h"
 #if defined(TARGET_ARCH_MIPS)
 
 #include "vm/isolate.h"
 #include "vm/dart_entry.h"
 #include "vm/native_entry.h"
@@ skipping 26 matching lines @@
   return &function;
 }
 
 
 // Test calls to stub code which calls into the runtime.
 static void GenerateCallToCallRuntimeStub(Assembler* assembler,
                                           int value1, int value2) {
   const int argc = 2;
   const Smi& smi1 = Smi::ZoneHandle(Smi::New(value1));
   const Smi& smi2 = Smi::ZoneHandle(Smi::New(value2));
-  const Object& result = Object::ZoneHandle();
   const Context& context = Context::ZoneHandle(Context::New(0, Heap::kOld));
   ASSERT(context.isolate() == Isolate::Current());
   __ EnterDartFrame(0);
   __ LoadObject(CTX, context);
-  __ PushObject(result);  // Push Null object for return value.
+  __ PushObject(Object::null_object());  // Push Null object for return value.
   __ PushObject(smi1);  // Push argument 1 smi1.
   __ PushObject(smi2);  // Push argument 2 smi2.
   ASSERT(kTestSmiSubRuntimeEntry.argument_count() == argc);
   __ CallRuntime(kTestSmiSubRuntimeEntry, argc);  // Call SmiSub runtime func.
   __ addiu(SP, SP, Immediate(argc * kWordSize));
   __ Pop(V0);  // Pop return value from return slot.
   __ LeaveDartFrameAndReturn();
 }
 
 
@@ skipping 41 matching lines @@
       *CreateFunction("Test_CallLeafRuntimeStubCode"), &_assembler_));
   const Function& function = RegisterFakeFunction(kName, code);
   Smi& result = Smi::Handle();
   result ^= DartEntry::InvokeFunction(function, Object::empty_array());
   EXPECT_EQ((value1 + value2), result.Value());
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_MIPS