Fix unused var warning.

runtime/vm/object_test.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 "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/bigint_operations.h"
 #include "vm/isolate.h"
 #include "vm/object.h"
 #include "vm/object_store.h"
@@ skipping 587 matching lines @@
     EXPECT(!str16.IsFourByteString());
     EXPECT_EQ(0x0000, str16.CharAt(0));
     EXPECT_EQ(0x7FFF, str16.CharAt(1));
     EXPECT_EQ(0xFFFF, str16.CharAt(2));
   }
 }
 
 
 TEST_CASE(StringFormat) {
   const char* hello_str = "Hello World!";
-  int32_t hello_len = strlen(hello_str);
   const String& str =
       String::Handle(String::NewFormatted("Hello %s!", "World"));
   EXPECT(str.IsInstance());
   EXPECT(str.IsString());
   EXPECT(str.IsOneByteString());
   EXPECT(!str.IsTwoByteString());
   EXPECT(!str.IsFourByteString());
   EXPECT(!str.IsNumber());
   EXPECT(str.Equals(hello_str));
 }
@@ skipping 2181 matching lines @@
   EXPECT_EQ(2, test_classes.length());
   EXPECT_EQ(smi_class.raw(), test_classes[0]->raw());
   EXPECT_EQ(smi_class.raw(), test_classes[1]->raw());
   EXPECT_EQ(target1.raw(), test_target.raw());
 }
 
 
 #endif  // defined(TARGET_ARCH_IA32) || defined(TARGET_ARCH_X64).
 
 }  // namespace dart