process_singleton_posix: Remove the singleton lock file is not a symlink

chrome/browser/process_singleton_posix.cc

 // Copyright 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.
 
 // On Linux, when the user tries to launch a second copy of chrome, we check
 // for a socket in the user's profile directory.  If the socket file is open we
 // send a message to the first chrome browser process with the current
 // directory and second process command line flags.  The second process then
 // exits.
 //
@@ skipping 261 matching lines @@
     }
   }
   return true;
 }
 
 // Extract the hostname and pid from the lock symlink.
 // Returns true if the lock existed.
 bool ParseLockPath(const base::FilePath& path,
                    std::string* hostname,
                    int* pid) {
+  // The lock file should be a symlink, not a regular file or a directory.
+  if (base::PathExists(path) && !base::IsLink(path)) {
+      base::DeleteFile(path, true);
+      return false;
+  }
+
   std::string real_path = ReadLink(path).value();
   if (real_path.empty())
     return false;
 
   std::string::size_type pos = real_path.rfind(kLockDelimiter);
 
   // If the path is not a symbolic link, or doesn't contain what we expect,
   // bail.
   if (pos == std::string::npos) {
     *hostname = "";
@@ skipping 763 matching lines @@
 }
 
 void ProcessSingleton::KillProcess(int pid) {
   // TODO(james.su@gmail.com): Is SIGKILL ok?
   int rv = kill(static_cast<base::ProcessHandle>(pid), SIGKILL);
   // ESRCH = No Such Process (can happen if the other process is already in
   // progress of shutting down and finishes before we try to kill it).
   DCHECK(rv == 0 || errno == ESRCH) << "Error killing process: "
                                     << base::safe_strerror(errno);
 }