Add a console control handler chrome_watcher.dll.

chrome/chrome_watcher/chrome_watcher_main.cc

 // Copyright (c) 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 <windows.h>
 
 #include "base/at_exit.h"
 #include "base/command_line.h"
 #include "base/logging_win.h"
 #include "base/process/process.h"
+#include "base/synchronization/waitable_event.h"
 #include "base/template_util.h"
 #include "components/browser_watcher/exit_code_watcher_win.h"
 #include "components/browser_watcher/exit_funnel_win.h"
 #include "components/browser_watcher/watcher_main_api_win.h"
 
 namespace {
 
 // Use the same log facility as Chrome for convenience.
 // {7FE69228-633E-4f06-80C1-527FEA23E3A7}
 const GUID kChromeWatcherTraceProviderName = {
     0x7fe69228, 0x633e, 0x4f06,
         { 0x80, 0xc1, 0x52, 0x7f, 0xea, 0x23, 0xe3, 0xa7 } };
 
+// The data shared from the main function to the console handler.
+struct HandlerData {
+  HandlerData() : handler_done(true, false) {}
+
+  base::WaitableEvent handler_done;
+  base::ProcessHandle process;
+  const base::char16* registry_path;
+};
+HandlerData *handler_data = NULL;
+
+static BOOL CALLBACK ConsoleCtrlHandler(DWORD ctl_type) {
+  if (handler_data && ctl_type == CTRL_LOGOFF_EVENT) {
+    // Record the watcher logoff event in the browser's exit funnel.
+    browser_watcher::ExitFunnel funnel;
+    funnel.Init(handler_data->registry_path, handler_data->process);
+    funnel.RecordEvent(L"WatcherLogoff");
+
+    // Release the main function.
+    handler_data->handler_done.Signal();
+  }
+
+  // Fall through to the next handler in turn.
+  return FALSE;
+}
+
 }  // namespace
 
+
 // The main entry point to the watcher, declared as extern "C" to avoid name
 // mangling.
 extern "C" int WatcherMain(const base::char16* registry_path) {
   // The exit manager is in charge of calling the dtors of singletons.
   base::AtExitManager exit_manager;
   // Initialize the commandline singleton from the environment.
   base::CommandLine::Init(0, NULL);
 
   logging::LogEventProvider::Initialize(kChromeWatcherTraceProviderName);
 
   // Arrange to be shut down as late as possible, as we want to outlive
   // chrome.exe in order to report its exit status.
   // TODO(siggi): Does this (windowless) process need to register a console
   //     handler too, in order to get notice of logoff events?
   ::SetProcessShutdownParameters(0x100, SHUTDOWN_NORETRY);
 
   browser_watcher::ExitCodeWatcher exit_code_watcher(registry_path);
   int ret = 1;
   // Attempt to wait on our parent process, and record its exit status.
   if (exit_code_watcher.ParseArguments(
         *base::CommandLine::ForCurrentProcess())) {
+    // Set up a console control handler, and provide it the data it needs
+    // to record into the browser's exit funnel.
+    HandlerData data;
+    data.process = exit_code_watcher.process().Handle();
+    data.registry_path = registry_path;
+    handler_data = &data;
+    ::SetConsoleCtrlHandler(ConsoleCtrlHandler, TRUE);
+
     // Wait on the process.
     exit_code_watcher.WaitForExit();
 
     browser_watcher::ExitFunnel funnel;
     funnel.Init(registry_path, exit_code_watcher.process().Handle());
     funnel.RecordEvent(L"BrowserExit");
 
+    // Wait for a max of 30 seconds to see whether we get notified of logoff.
+    data.handler_done.TimedWait(base::TimeDelta::FromSeconds(30));

[erikwright (departed), 2014/12/18 21:45:07]

This wait is problematic. During an uninstall it could cause the user to be
prompted to "Exit Chrome" when they have already done so. I don't think we can
do this.

[Sigurður Ásgeirsson, 2014/12/18 21:50:33]

This is a good point. While this isn't intended as a permanent feature, perhaps
it's better to tardy only for trouble exception codes?

+
+    // Remove the console control handler.
+    // There is a potential race here, where the handler might be executing
+    // already as we fall through here. Hopefully SetConsoleCtrlHandler is
+    // synchronizing against handler execution, for there's no other way to
+    // close the race. Thankfully we'll just get snuffed out, as this is logoff.
+    ::SetConsoleCtrlHandler(ConsoleCtrlHandler, FALSE);
+    handler_data = NULL;
+
     ret = 0;
   }
 
   // Wind logging down.
   logging::LogEventProvider::Uninitialize();
 
   return ret;
 }
 
 static_assert(base::is_same<decltype(&WatcherMain),
                             browser_watcher::WatcherMainFunction>::value,
               "WatcherMain() has wrong type");