Add installer::SetupSingleton.

chrome/installer/setup/setup_singleton.h

Index: chrome/installer/setup/setup_singleton.h
diff --git a/chrome/installer/setup/setup_singleton.h b/chrome/installer/setup/setup_singleton.h
new file mode 100644
index 0000000000000000000000000000000000000000..cdfd0fceefab056cd404e3f37478ded35a12951e
--- /dev/null
+++ b/chrome/installer/setup/setup_singleton.h
@@ -0,0 +1,92 @@
+// 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 CHROME_INSTALLER_SETUP_SETUP_SINGLETON_H_
+#define CHROME_INSTALLER_SETUP_SETUP_SINGLETON_H_
+
+#include <windows.h>
+
+#include <memory>
+
+#include "base/macros.h"
+#include "base/strings/string16.h"
+#include "base/synchronization/waitable_event.h"
+#include "base/win/scoped_handle.h"
+
+namespace base {
+class CommandLine;
+class TimeDelta;
+}
+
+namespace installer {
+
+class InstallationState;
+class InstallerState;
+class MasterPreferences;
+
+// Any modification to a Chrome installation should be done within the scope of
+// a SetupSingleton. There can be only one active SetupSingleton per Chrome
+// installation at a time.
+class SetupSingleton {
+ public:
+  // Returns a SetupSingleton which, throughout its lifetime, gives to the

[grt (UTC plus 2), 2016/09/01 12:05:39]

language nit "to the" -> "the"

[fdoray, 2016/09/01 15:45:23]

Done.

+  // current process the exclusive right to modify the Chrome installation
+  // described by |installer_state| (installation directory and associated
+  // registry keys). May block. |installer_state| and |original_state| are
+  // updated using |command_line| and  just before this returns in case the

[grt (UTC plus 2), 2016/09/01 12:05:39]

"and |master_preferences|"?

[grt (UTC plus 2), 2016/09/01 12:05:39]

maybe change to something like "...updated using ... to reflect the new state of
the installation after acquisition."

[fdoray, 2016/09/01 15:45:23]

Done.

[fdoray, 2016/09/01 15:45:23]

Done.

+  // Chrome installation was
+  // modified by another process before the exclusive right to modify it was
+  // acquired. Returns nullptr on failure.
+  static std::unique_ptr<SetupSingleton> Acquire(
+      const base::CommandLine& command_line,
+      const MasterPreferences& master_preferences,
+      InstallerState* installer_state,
+      InstallationState* original_state);
+
+  // Releases the exclusive right to modifiy the Chrome installation.
+  ~SetupSingleton();
+
+  // Waits until |max_time| has passed or someone tries to acquire a

[grt (UTC plus 2), 2016/09/01 12:05:39]

"someone" -> "another process"

[fdoray, 2016/09/01 15:45:23]

Done.

+  // SetupSingleton for the same Chrome installation as this SetupSingleton. In

[grt (UTC plus 2), 2016/09/01 12:05:39]

nit: omit " as this SetupSingleton". i think it's implied.

[fdoray, 2016/09/01 15:45:23]

Done.

+  // the latter case, the method returns true and this SetupSingleton should be
+  // released as soon as possible to unblock the acquisition of the other
+  // SetupSingleton.
+  bool Wait(const base::TimeDelta& max_time);

[grt (UTC plus 2), 2016/09/01 12:05:39]

how about WaitForInterrupt?

[fdoray, 2016/09/01 15:45:23]

Done.

+
+ private:
+  class ScopedHoldMutex {
+   public:
+    ScopedHoldMutex();
+    ~ScopedHoldMutex();
+
+    // Waits up to a certain amount of time to acquire |mutex|. Returns true on
+    // success. |mutex| will be released in the destructor.
+    bool Acquire(HANDLE mutex);
+
+   private:
+    HANDLE mutex_ = INVALID_HANDLE_VALUE;
+
+    DISALLOW_COPY_AND_ASSIGN(ScopedHoldMutex);
+  };
+
+  // |sync_primitive_name_suffix| is a suffix for the name of |setup_mutex_| and
+  // |exit_event_|.
+  explicit SetupSingleton(const base::string16& sync_primitive_name_suffix);
+
+  // A mutex that must be held to modify the Chrome installation directory.
+  base::win::ScopedHandle setup_mutex_;
+
+  // Holds |setup_mutex_| throughout the lifetime of this SetupSingleton.
+  ScopedHoldMutex scoped_hold_setup_mutex_;
+
+  // An event signaled to ask the owner of |setup_mutex_| to release it as soon
+  // as possible.
+  base::WaitableEvent exit_event_;
+
+  DISALLOW_COPY_AND_ASSIGN(SetupSingleton);
+};
+
+}  // namespace installer
+
+#endif  // CHROME_INSTALLER_SETUP_SETUP_SINGLETON_H_