Make application shortcuts point to app_host.exe, install App Host during app installation.

chrome/browser/extensions/app_host_installer_impl_win.cc

+// Copyright (c) 2012 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/browser/extensions/app_host_installer_impl_win.h"
+
+#include <windows.h>
+#include "base/basictypes.h"
+#include "base/bind.h"
+#include "base/callback.h"
+#include "base/logging.h"
+#include "base/process_util.h"
+#include "base/string16.h"
+#include "base/win/object_watcher.h"
+#include "base/win/registry.h"
+#include "chrome/browser/extensions/app_host_installer.h"
+#include "chrome/installer/launcher_support/chrome_launcher_support.h"
+#include "content/public/browser/browser_thread.h"
+
+namespace {
+
+// TODO(huangs) Refactor the constants: http://crbug.com/148538
+const wchar_t kGoogleRegClientsKey[] = L"Software\\Google\\Update\\Clients";
+
+// Copied from chrome_appid.cc.
+const wchar_t kBinariesAppGuid[] = L"{4DC8B4CA-1BDA-483e-B5FA-D3C12E15B62D}";
+
+// Copied from google_update_constants.cc
+const wchar_t kRegCommandLineField[] = L"CommandLine";
+const wchar_t kRegCommandsKey[] = L"Commands";
+
+// Copied from util_constants.cc.
+const wchar_t kCmdQuickEnableApplicationHost[] =
+    L"quick-enable-application-host";
+
+// QuickEnableDelegate handles the completion event of App Host installation
+// via the quick-enable-application host command.  At construction, the
+// class is given |callback_| that takes a bool parameter.
+// Upon completion, |callback_| is invoked, and is passed a boolean to
+// indicate success or failure of installation.
+class QuickEnableDelegate : public base::win::ObjectWatcher::Delegate {
+ public:
+  QuickEnableDelegate(const base::Callback<void(bool)>& callback)
+      : callback_(callback) {}
+
+  // base::win::ObjectWatcher::Delegate implementation.
+  virtual void OnObjectSignaled(HANDLE object) OVERRIDE {
+    int exit_code = 0;
+    base::TerminationStatus status(
+        base::GetTerminationStatus(object, &exit_code));
+    if (status == base::TERMINATION_STATUS_NORMAL_TERMINATION) {
+      callback_.Run(true);
+    } else {
+      LOG(ERROR) << "App Host install failed, status = " << status
+                 << ", exit code = " << exit_code;
+      callback_.Run(false);
+    }
+    callback_.Reset();
+  }
+
+ private:
+  base::Callback<void(bool)> callback_;
+
+  DISALLOW_COPY_AND_ASSIGN(QuickEnableDelegate);
+};
+
+// Reads the path to app_host.exe from the value "UninstallString" within the
+// App Host's "ClientState" registry key.  Returns an empty string if the path
+// does not exist or cannot be read.
+string16 GetQuickEnableAppHostCommand(bool system_level) {
+  HKEY root_key = system_level ? HKEY_LOCAL_MACHINE : HKEY_CURRENT_USER;
+  string16 subkey(kGoogleRegClientsKey);
+  subkey.append(1, L'\\').append(kBinariesAppGuid)
+      .append(1, L'\\').append(kRegCommandsKey)
+      .append(1, L'\\').append(kCmdQuickEnableApplicationHost);
+  base::win::RegKey reg_key;
+  string16 cmd;
+  if (reg_key.Open(root_key, subkey.c_str(),
+                   KEY_QUERY_VALUE) == ERROR_SUCCESS) {
+    // If read is unsuccessful, |cmd| remains empty.
+    reg_key.ReadValue(kRegCommandLineField, &cmd);
+  }
+  return cmd;
+}
+
+// Launches the Google Update command to quick-enable App Host.
+// Returns true if the command is launched.
+bool LaunchQuickEnableAppHost(base::win::ScopedHandle* process) {
+  DCHECK(!process->IsValid());
+  bool success = false;
+
+  string16 cmd_str(GetQuickEnableAppHostCommand(true));
+  if (cmd_str.empty())  // Try user-level if absent from system-level.
+    cmd_str = GetQuickEnableAppHostCommand(false);
+  if (!cmd_str.empty()) {
+    VLOG(1) << "Quick-enabling application host: " << cmd_str;
+    if (!base::LaunchProcess(cmd_str, base::LaunchOptions(),
+                             process->Receive())) {
+      LOG(ERROR) << "Failed to quick-enable application host.";
+    }
+    success = process->IsValid();
+  }
+  return success;
+}
+
+}  // namespace
+
+namespace extensions {
+
+namespace app_host_installer {
+
+using content::BrowserThread;
+
+// static function.

[erikwright (departed), 2012/10/09 21:51:52]

just "// static"

[huangs, 2012/10/09 22:44:26]

Done.

+void AppHostInstallerImpl::EnsureAppHostInstalled(
+    const base::Callback<void(bool)>& completion_callback) {
+  BrowserThread::ID caller_thread_id;
+  if (!BrowserThread::GetCurrentThreadIdentifier(&caller_thread_id)) {
+    NOTREACHED();
+    return;
+  }
+
+  AppHostInstallerImpl *impl =

[erikwright (departed), 2012/10/09 21:51:52]

the assignment to a local variable is unnecessary.

[huangs, 2012/10/09 22:44:26]

Done.  Needed (new ...)->... to make compiler happy.

+      new AppHostInstallerImpl(completion_callback, caller_thread_id);
+  impl->EnsureAppHostInstalledInternal();
+  // impl will delete itself.

[erikwright (departed), 2012/10/09 21:51:52]

// AppHostInstalerImpl will delete itself
new AppHostInstallerImpl(...)->EnsureAppHostInstalledInternal();

[huangs, 2012/10/09 22:44:26]

Done.

+}
+
+// AppHostInstallerImpl checks the presence of app_host.exe, and launches

[erikwright (departed), 2012/10/09 21:51:52]

This comment should probably be at the top of this file.

Fully-qualify Finish (AppHostInstallerImpl::Finish) and instead of
|completion_callback| just say "which notifies the caller via a completion
callback on the original calling thread and then destroys the
AppHostInstallerImpl instance."

[huangs, 2012/10/09 22:44:26]

Done.

+// the installer if missing. The check must be performed on the FILE thread.
+// The installation is also launched on the FILE thread as an asynchronous
+// process. Once installation completes, QuickEnableWatcher is notified.
+// Finish() is called in the end, which returns to the caller thread and
+// calls |completion_callback|, followed by self-destruction.
+
+// Private constructor.
+AppHostInstallerImpl::AppHostInstallerImpl(

[erikwright (departed), 2012/10/09 21:51:52]

"// Private constructor." is not necessary.

[huangs, 2012/10/09 22:44:26]

Done.

+    const base::Callback<void(bool)>& completion_callback,
+    BrowserThread::ID caller_thread_id)
+    : completion_callback_(completion_callback),
+      caller_thread_id_(caller_thread_id) {}
+
+// Private destructor.

[erikwright (departed), 2012/10/09 21:51:52]

not necessary.

[huangs, 2012/10/09 22:44:26]

Done.

+AppHostInstallerImpl::~AppHostInstallerImpl() {}
+
+// Checks the system state on the FILE thread. Will trigger InstallAppHost()

[erikwright (departed), 2012/10/09 21:51:52]

Unless you have implementation details to add beyond what is in the header, no
comment is necessary here.

[huangs, 2012/10/09 22:44:26]

Done.

+// if App Host is not installed.
+void AppHostInstallerImpl::EnsureAppHostInstalledInternal() {
+  if (!BrowserThread::CurrentlyOn(BrowserThread::FILE)) {
+    // Redo on FILE thread.
+    if (!BrowserThread::PostTask(BrowserThread::FILE, FROM_HERE,
+            base::Bind(&AppHostInstallerImpl::EnsureAppHostInstalledInternal,
+                       base::Unretained(this)))) {
+      Finish(false);
+    }
+    return;
+  }
+
+  if (chrome_launcher_support::IsAppHostPresent())
+    Finish(true);
+  else
+    InstallAppHost();
+}
+
+// Asynchronously triggers the App Host installation. Will call "Finish" upon

[erikwright (departed), 2012/10/09 21:51:52]

Ditto.

[huangs, 2012/10/09 22:44:26]

Done. Moved the comment to the .h file.

+// completion (successful or otherwise).
+void AppHostInstallerImpl::InstallAppHost() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  DCHECK(!process_.IsValid());
+  if (!LaunchQuickEnableAppHost(&process_)) {
+    Finish(false);
+  } else {
+    DCHECK(process_.IsValid());
+    DCHECK(!delegate_.get());
+    watcher_.StopWatching();
+    delegate_.reset(new QuickEnableDelegate(
+        base::Bind(&AppHostInstallerImpl::Finish, base::Unretained(this))));
+    watcher_.StartWatching(process_, delegate_.get());
+  }
+}
+
+// Passes |success| to |completion_callback| on the original caller thread.

[erikwright (departed), 2012/10/09 21:51:52]

Ditto.

[huangs, 2012/10/09 22:44:26]

Done.

+// Deletes the AppHostInstallerImpl.
+void AppHostInstallerImpl::Finish(bool success) {
+  if (!BrowserThread::CurrentlyOn(caller_thread_id_)) {
+    // Redo on caller thread.
+    if (!BrowserThread::PostTask(caller_thread_id_, FROM_HERE, base::Bind(
+            &AppHostInstallerImpl::Finish, base::Unretained(this), success))) {
+      // This could happen in Shutdown....
+      delete this;
+    }
+    return;
+  }
+
+  completion_callback_.Run(success);
+  delete this;
+}
+
+}  // namespace app_host_installer
+
+}  // namespace extensions