Clean up MojoShellConnection in render processes

mojo/shell/runner/host/child_process_host.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/shell/runner/host/child_process_host.h"
 
 #include <stdint.h>
 
 #include <utility>
 
@@ skipping 67 matching lines @@
       base::Bind(&ChildProcessHost::DoLaunch, base::Unretained(this)),
       base::Bind(&ChildProcessHost::DidStart,
                  weak_factory_.GetWeakPtr(), callback));
 }
 
 int ChildProcessHost::Join() {
   if (controller_)  // We use this as a signal that Start was called.
     start_child_process_event_.Wait();
 
   controller_ = mojom::ChildControllerPtr();
-  DCHECK(child_process_.IsValid());
+  // This host may be hosting a child process whose lifetime is controlled
+  // elsewhere. In this case we have no known process handle to wait on.
+  if (child_process_.IsValid()) {
+    int rv = -1;
+    LOG_IF(ERROR, !child_process_.WaitForExit(&rv))
+        << "Failed to wait for child process";
 
-  int rv = -1;
-  LOG_IF(ERROR, !child_process_.WaitForExit(&rv))
-      << "Failed to wait for child process";
+    child_process_.Close();
+    return rv;
+  }
 
-  child_process_.Close();
-
-  return rv;
+  return 0;
 }
 
 void ChildProcessHost::StartApp(
     InterfaceRequest<mojom::ShellClient> request,
     const mojom::ChildController::StartAppCallback& on_app_complete) {
   DCHECK(controller_);
 
+  // In this case the process must have already been launched.
+  start_child_process_event_.Signal();
+
   on_app_complete_ = on_app_complete;
   controller_->StartApp(
       std::move(request),
       base::Bind(&ChildProcessHost::AppCompleted, weak_factory_.GetWeakPtr()));
 }
 
 void ChildProcessHost::ExitNow(int32_t exit_code) {
   DCHECK(controller_);
 
   controller_->ExitNow(exit_code);
@@ skipping 111 matching lines @@
 void ChildProcessHost::AppCompleted(int32_t result) {
   if (!on_app_complete_.is_null()) {
     auto on_app_complete = on_app_complete_;
     on_app_complete_.reset();
     on_app_complete.Run(result);
   }
 }
 
 }  // namespace shell
 }  // namespace mojo