Don't read Linux host configuration if binary is not on path.

remoting/host/plugin/daemon_controller.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 REMOTING_HOST_DAEMON_CONTROLLER_H_
 #define REMOTING_HOST_DAEMON_CONTROLLER_H_
 
 #include <string>
 
 #include "base/callback_forward.h"
@@ skipping 47 matching lines @@
     // TODO(sergeyu): Current implementations don't return this value.
     RESULT_CANCELLED = 2,
 
     // Failed to access host directory.
     RESULT_FAILED_DIRECTORY = 3
 
     // TODO(sergeyu): Add more error codes when we know how to handle
     // them in the webapp.
   };
 
-  // The callback for GetConfig(). |config| is set to NULL in case of
-  // an error. Otherwise it is a dictionary that contains only the
-  // following values: host_id and xmpp_login, which may be empty if
-  // the host is not initialized yet. All other values are filtered out of the
-  // config before this callback is invoked: they may contain security
-  // sensitive information, such as authentication tokens and private keys.
+  // Callback type for GetConfig(). If the host is configured then a dictionary
+  // is returned containing host_id and xmpp_login, with security-sensitive
+  // fields filtered out. An empty dictionary is returned if the host is not
+  // configured, and NULL if the configuration is corrupt or cannot be read.
   typedef base::Callback<void (scoped_ptr<base::DictionaryValue> config)>
       GetConfigCallback;
 
   // Callback used for asynchronous operations, e.g. when
   // starting/stopping the service.
   typedef base::Callback<void (AsyncResult result)> CompletionCallback;
 
   virtual ~DaemonController() {}
 
   // Return the "installed/running" state of the daemon process.
@@ skipping 39 matching lines @@
   // Caches the native handle of the plugin window so it can be used to focus
   // elevation prompts properly.
   virtual void SetWindow(void* window_handle) = 0;
 
   static scoped_ptr<DaemonController> Create();
 };
 
 }  // namespace remoting
 
 #endif  // REMOTING_HOST_DAEMON_CONTROLLER_H_