Revise comments on various Shell interfaces. Make some methods private on ShellConnection.

mojo/shell/public/cpp/lib/app_lifetime_helper.cc

 // Copyright 2015 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/shell/public/cpp/app_lifetime_helper.h"
 
 #include "base/bind.h"
 #include "base/message_loop/message_loop.h"
 #include "mojo/shell/public/cpp/shell_connection.h"
 
@@ skipping 45 matching lines @@
     DCHECK(clone_task_runner_->BelongsToCurrentThread());
   } else {
     clone_task_runner_ = base::MessageLoop::current()->task_runner();
   }
 #endif
 
   return make_scoped_ptr(new AppRefCount(
       app_lifetime_helper_, app_task_runner_));
 }
 
-AppLifetimeHelper::AppLifetimeHelper(ShellConnection* app)
-    : app_(app), ref_count_(0) {
+AppLifetimeHelper::AppLifetimeHelper(Shell* shell)
+    : shell_(shell), ref_count_(0) {
 }
 
 AppLifetimeHelper::~AppLifetimeHelper() {
 }
 
 scoped_ptr<AppRefCount> AppLifetimeHelper::CreateAppRefCount() {
   AddRef();
   return make_scoped_ptr(new AppRefCount(
       this, base::MessageLoop::current()->task_runner()));
 }
 
 void AppLifetimeHelper::AddRef() {
   ref_count_++;
 }
 
 void AppLifetimeHelper::Release() {
   if (!--ref_count_) {
-    if (app_)
-      app_->Quit();
+    if (shell_)
+      shell_->Quit();
   }
 }
 
 void AppLifetimeHelper::OnQuit() {
-  app_ = nullptr;
+  shell_ = nullptr;
 }
 
 }  // namespace mojo