For the out-of-process NativeRunner, make sure that Start()'s callback always gets called.

shell/application_manager/native_runner.h

 // 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.
 
 #ifndef SHELL_APPLICATION_MANAGER_NATIVE_RUNNER_H_
 #define SHELL_APPLICATION_MANAGER_NATIVE_RUNNER_H_
 
 #include "base/callback_forward.h"
 #include "base/memory/scoped_ptr.h"
 #include "mojo/public/cpp/bindings/interface_request.h"
 #include "mojo/public/interfaces/application/application.mojom.h"
 #include "shell/native_application_support.h"
 
 namespace base {
 class FilePath;
 }
 
 namespace mojo {
 namespace shell {
 
 // ApplicationManager requires implementations of NativeRunner and
 // NativeRunnerFactory to run native applications.
 class NativeRunner {
  public:
   virtual ~NativeRunner() {}
 
   // Loads the app in the file at |app_path| and runs it on some other
   // thread/process. If |cleanup| is |DELETE|, this takes ownership of the file.
   // |app_completed_callback| is posted (to the thread on which |Start()| was
-  // called) after |MojoMain()| completes.
+  // called) after |MojoMain()| completes, or on any error (including if it
+  // fails to start).
   // TODO(vtl): |app_path| and |cleanup| should probably be moved to the
   // factory's Create(). Rationale: The factory may need information from the
   // file to decide what kind of NativeRunner to make.
   virtual void Start(const base::FilePath& app_path,
                      NativeApplicationCleanup cleanup,
                      InterfaceRequest<Application> application_request,
                      const base::Closure& app_completed_callback) = 0;
 };
 
 class NativeRunnerFactory {
  public:
   // Options for running the native app. (This will contain, e.g., information
   // about the sandbox profile, etc.)
   struct Options {
     // Constructs with default options.
     Options() : force_in_process(false) {}
 
     bool force_in_process;
   };
 
   virtual ~NativeRunnerFactory() {}
   virtual scoped_ptr<NativeRunner> Create(const Options& options) = 0;
 };
 
 }  // namespace shell
 }  // namespace mojo
 
 #endif  // SHELL_APPLICATION_MANAGER_NATIVE_RUNNER_H_