Adds a way to associate key/value pairs with the environment

mojo/public/cpp/environment/lib/environment.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "mojo/public/cpp/environment/environment.h"
 
 #include "mojo/public/cpp/environment/lib/buffer_tls_setup.h"
 #include "mojo/public/cpp/utility/run_loop.h"
 
 namespace mojo {
 
-Environment::Environment() {
+Environment::Environment() : data_(NULL) {
   internal::SetUpCurrentBuffer();
   RunLoop::SetUp();
 }
 
 Environment::~Environment() {
   RunLoop::TearDown();
   internal::TearDownCurrentBuffer();
 }
 
 }  // namespace mojo