Introduce the ability to wait for the watcher process to initialize.

chrome/app/chrome_watcher_client_win.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 "chrome/app/chrome_watcher_client_win.h"
+
+#include "base/bind.h"
+#include "base/logging.h"
+#include "components/browser_watcher/watcher_client_win.h"
+
+namespace {
+
+// Because we can only bind parameters from the left, |parent_process| must be
+// the last parameter of the method that we bind int a
+// BrowserWatcherClient::CommandLineGenerator. The ChromeWatcherClient API is
+// more intuitive if the ChromeWatcherClient::CommandLineGenerator takes
+// |parent_process| as its second (of three) parameters, so we use this
+// intermediate function to swap the order.
+base::CommandLine InvokeCommandLineGenerator(
+    const ChromeWatcherClient::CommandLineGenerator& command_line_generator,
+    HANDLE on_initialized_event,
+    HANDLE parent_process) {
+  return command_line_generator.Run(parent_process, on_initialized_event);
+}
+
+}  // namespace
+
+ChromeWatcherClient::ChromeWatcherClient(
+    const CommandLineGenerator& command_line_generator)
+    : command_line_generator_(command_line_generator) {
+}
+
+ChromeWatcherClient::~ChromeWatcherClient() {
+}
+
+bool ChromeWatcherClient::LaunchWatcher() {
+  // Create an inheritable event that the child process will signal when it has
+  // completed initialization.
+  SECURITY_ATTRIBUTES on_initialized_event_attributes = {
+      sizeof(SECURITY_ATTRIBUTES),  // nLength
+      nullptr,                      // lpSecurityDescriptor
+      TRUE                          // bInheritHandle
+  };
+  on_initialized_event_.Set(::CreateEvent(&on_initialized_event_attributes,
+                                          TRUE,  // manual reset
+                                          FALSE, nullptr));
+  if (!on_initialized_event_.IsValid()) {
+    DPLOG(ERROR) << "Failed to create an event.";
+    return false;
+  }
+
+  // Configure the basic WatcherClient, binding in the initialization event
+  // HANDLE.
+  browser_watcher::WatcherClient watcher_client(
+      base::Bind(&InvokeCommandLineGenerator, command_line_generator_,
+                 on_initialized_event_.Get()));
+  // Indicate that the event HANDLE should be inherited.
+  watcher_client.AddInheritedHandle(on_initialized_event_.Get());
+  // Launch the watcher.
+  watcher_client.LaunchWatcher();
+  // Grab a handle to the watcher so that we may later wait on its
+  // initialization.
+  process_ = watcher_client.process().Duplicate();
+  if (!process_.IsValid())
+    on_initialized_event_.Close();
+  return process_.IsValid();
+}
+
+bool ChromeWatcherClient::EnsureInitialized() {
+  if (!process_.IsValid())
+    return false;
+
+  DCHECK(on_initialized_event_.IsValid());
+
+  HANDLE handles[] = {on_initialized_event_.Get(), process_.Handle()};
+  DWORD result = ::WaitForMultipleObjects(arraysize(handles), handles,
+                                          FALSE, INFINITE);
+
+  switch (result) {
+    case WAIT_OBJECT_0:
+      return true;
+    case WAIT_OBJECT_0 + 1:
+      LOG(ERROR) << "Chrome watcher process failed to launch.";
+      return false;
+    case WAIT_FAILED:
+      DPLOG(ERROR) << "Failure while waiting on Chrome watcher process launch.";
+      return false;
+    default:
+      NOTREACHED() << "Unexpected result while waiting on Chrome watcher "
+                      "process launch: " << result;
+      return false;
+  }
+}
+
+bool ChromeWatcherClient::WaitForExit(int* exit_code) {
+  return process_.IsValid() && process_.WaitForExit(exit_code);
+}
+
+bool ChromeWatcherClient::WaitForExitWithTimeout(base::TimeDelta timeout,
+                                                 int* exit_code) {
+  return process_.IsValid() &&
+         process_.WaitForExitWithTimeout(timeout, exit_code);
+}