Add a mojo::RunApplication() for running implementations of ApplicationImplBase.

mojo/public/cpp/application/run_application.h

+// Copyright 2016 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 MOJO_PUBLIC_CPP_APPLICATION_RUN_APPLICATION_H_
+#define MOJO_PUBLIC_CPP_APPLICATION_RUN_APPLICATION_H_
+
+#include "mojo/public/c/system/handle.h"
+#include "mojo/public/c/system/result.h"
+
+namespace mojo {
+
+class ApplicationImplBase;
+
+// Sets up a message (run) loop and runs the provided application
+// implementation.
+//
+// Typical use (where |MyApplicationImpl| is an implementation of
+// |ApplicationImplBase|):
+//
+//   MojoResult MojoMain(MojoHandle application_request_handle) {
+//     MyApplicationImpl my_app;
+//     mojo::RunApplication(application_request_handle, &my_app);
+//     return MOJO_RESULT_OK;
+//   }
+//
+// Note that this may actually be used on any thread (that is not already
+// running a message loop of some sort).
+//
+// |*application_impl| must remain alive until the message loop starts running
+// (thus it may own itself).
+//
+// TODO(vtl): Possibly this should return a |MojoResult| and
+// |TerminateApplication()| should take a |MojoResult| argument (which this
+// returns), but to communicate that value requires TLS.
+// TODO(vtl): Maybe this should be like |Environment|, with different possible
+// implementations (e.g., "standalone" vs "chromium"). However,
+// |ApplicationRunnerChromium| currently has additional goop specific to the
+// main thread. Probably we should have additional "MainRunApplication()" and
+// "MainTerminateApplication()" functions.
+void RunApplication(MojoHandle application_request_handle,
+                    ApplicationImplBase* application_impl);
+
+// Terminates the currently-running application. This may only be called from
+// "inside" |RunApplication()| (i.e., it is on the stack, which means that the
+// message loop is running). This will cause |RunApplication()| to return "soon"
+// (assuming the message loop is not blocked processing some task). This may
+// cause queued work to *not* be executed.
+void TerminateApplication();
+
+}  // namespace mojo
+
+#endif  // MOJO_PUBLIC_CPP_APPLICATION_RUN_APPLICATION_H_