Refactor ProcessSingleton to allow a Desktop process to activate Metro Chrome cleanly.

chrome/browser/process_singleton.h

 // 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.
 
 #ifndef CHROME_BROWSER_PROCESS_SINGLETON_H_
 #define CHROME_BROWSER_PROCESS_SINGLETON_H_
 
 #include "build/build_config.h"
 
 #if defined(OS_WIN)
 #include <windows.h>
 #endif  // defined(OS_WIN)
 
 #include <set>
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/callback.h"
 #include "base/command_line.h"
 #include "base/file_path.h"
 #include "base/logging.h"
 #include "base/memory/ref_counted.h"
 #include "base/process.h"
 #include "base/threading/non_thread_safe.h"
 #include "ui/gfx/native_widget_types.h"
 
-#if defined(OS_POSIX)
-#include "base/file_path.h"
-#endif  // defined(OS_POSIX)
-
 #if defined(OS_LINUX) || defined(OS_OPENBSD)
 #include "base/files/scoped_temp_dir.h"
 #endif  // defined(OS_LINUX) || defined(OS_OPENBSD)
 
 class CommandLine;
-class FilePath;
 
 // ProcessSingleton ----------------------------------------------------------
 //
 // This class allows different browser processes to communicate with
 // each other.  It is named according to the user data directory, so
 // we can be sure that no more than one copy of the application can be
 // running at once with a given data directory.
 //
 // Implementation notes:
 // - the Windows implementation uses an invisible global message window;
@@ skipping 16 matching lines @@
   typedef base::Callback<
       bool(const CommandLine& command_line, const FilePath& current_directory)>
       NotificationCallback;
 
   explicit ProcessSingleton(const FilePath& user_data_dir);
   ~ProcessSingleton();
 
   // Notify another process, if available. Otherwise sets ourselves as the
   // singleton instance and stores the provided callback for notification from
   // future processes. Returns PROCESS_NONE if we became the singleton
-  // instance.
+  // instance. Callers are guaranteed to either have notified an existing
+  // process or have grabbed the singleton (unless the profile is locked by an
+  // unreachable process).
+  // TODO(brettw): Make the implementation of this method non-platform-specific
+  // by making Linux re-use the Windows implementation.
   NotifyResult NotifyOtherProcessOrCreate(
       const NotificationCallback& notification_callback);
 
   // Sets ourself up as the singleton instance.  Returns true on success.  If
   // false is returned, we are not the singleton instance and the caller must
   // exit. Otherwise, stores the provided callback for notification from
   // future processes.
   // NOTE: Most callers should generally prefer NotifyOtherProcessOrCreate() to
   // this method, only callers for whom failure is prefered to notifying another
   // process should call this directly.
@@ skipping 29 matching lines @@
 #if defined(OS_WIN)
   LRESULT WndProc(HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam);
 #endif
 
 #if defined(OS_LINUX) || defined(OS_OPENBSD)
   static void DisablePromptForTesting();
 #endif  // defined(OS_LINUX) || defined(OS_OPENBSD)
 
  protected:
   // Notify another process, if available.
-  // Returns true if another process was found and notified, false if we
-  // should continue with this process.
-  // Windows code roughly based on Mozilla.
-  //
-  // TODO(brettw): this will not handle all cases. If two processes start up too
-  // close to each other, the Create() might not yet have happened for the
-  // first one, so this function won't find it.
+  // Returns true if another process was found and notified, false if we should
+  // continue with the current process.
+  // On Windows, Create() has to be called before this.
   NotifyResult NotifyOtherProcess();
 
 #if defined(OS_LINUX) || defined(OS_OPENBSD)
   // Exposed for testing.  We use a timeout on Linux, and in tests we want
   // this timeout to be short.
   NotifyResult NotifyOtherProcessWithTimeout(const CommandLine& command_line,
                                              int timeout_seconds,
                                             bool kill_unresponsive);
   NotifyResult NotifyOtherProcessWithTimeoutOrCreate(
       const CommandLine& command_line,
@@ skipping 20 matching lines @@
 #if defined(OS_WIN)
   // This ugly behemoth handles startup commands sent from another process.
   LRESULT OnCopyData(HWND hwnd, const COPYDATASTRUCT* cds);
 
   bool EscapeVirtualization(const FilePath& user_data_dir);
 
   HWND remote_window_;  // The HWND_MESSAGE of another browser.
   HWND window_;  // The HWND_MESSAGE window.
   bool is_virtualized_;  // Stuck inside Microsoft Softricity VM environment.
   HANDLE lock_file_;
+  FilePath user_data_dir_;
 #elif defined(OS_LINUX) || defined(OS_OPENBSD)
   // Return true if the given pid is one of our child processes.
   // Assumes that the current pid is the root of all pids of the current
   // instance.
   bool IsSameChromeInstance(pid_t pid);
 
   // Extract the process's pid from a symbol link path and if it is on
   // the same host, kill the process, unlink the lock file and return true.
   // If the process is part of the same chrome instance, unlink the lock file
   // and return true without killing it.
@@ skipping 37 matching lines @@
 #endif
 
   // If messages are received in the locked state, the corresponding command
   // lines are saved here to be replayed later.
   std::vector<DelayedStartupMessage> saved_startup_messages_;
 
   DISALLOW_COPY_AND_ASSIGN(ProcessSingleton);
 };
 
 #endif  // CHROME_BROWSER_PROCESS_SINGLETON_H_