Fix out-of-bounds access in JSONStream test.

runtime/vm/json_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 "platform/json.h"
 #include "vm/json_stream.h"
 #include "vm/unit_test.h"
 #include "vm/dart_api_impl.h"
 
@@ skipping 384 matching lines @@
   const char* option_keys[] = {"dog", "cat"};
   const char* option_values[] = {"apple", "banana"};
 
   JSONStream js;
   EXPECT(js.num_arguments() == 0);
   js.SetArguments(&arguments[0], 3);
   EXPECT(js.num_arguments() == 3);
   EXPECT_STREQ("a", js.command());
 
   EXPECT(js.num_options() == 0);
-  js.SetOptions(&option_keys[0], &option_values[0], 3);
-  EXPECT(js.num_options() == 3);
+  js.SetOptions(&option_keys[0], &option_values[0], 2);
+  EXPECT(js.num_options() == 2);
   EXPECT(!js.HasOption("lizard"));
   EXPECT(js.HasOption("dog"));
   EXPECT(js.HasOption("cat"));
   EXPECT(js.OptionIs("cat", "banana"));
   EXPECT(!js.OptionIs("dog", "banana"));
 }
 
 }  // namespace dart