Use file handles to interact with utility process.

chrome/service/cloud_print/print_system.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_SERVICE_CLOUD_PRINT_PRINT_SYSTEM_H_
 #define CHROME_SERVICE_CLOUD_PRINT_PRINT_SYSTEM_H_
 
 #include <map>
 #include <string>
 #include <vector>
@@ skipping 56 matching lines @@
 // print system specific. For example, CUPS is available on both Linux and Mac,
 // but not available on ChromeOS, etc. This design allows us to add more
 // functionality on some platforms, while reusing core (CUPS) functions.
 class PrintSystem : public base::RefCountedThreadSafe<PrintSystem> {
  public:
   class PrintServerWatcher
       : public base::RefCountedThreadSafe<PrintServerWatcher> {
    public:
     // Callback interface for new printer notifications.
     class Delegate {
       public:

[Lei Zhang, 2014/09/15 21:49:53]

nit: actually this is indented 1 space too many.

[Vitaly Buka (NO REVIEWS), 2014/09/15 22:33:50]

Done.

-        virtual void OnPrinterAdded() = 0;
+       virtual void OnPrinterAdded() = 0;
         // TODO(gene): Do we need OnPrinterDeleted notification here?
 
       protected:
-        virtual ~Delegate() {}
+       virtual ~Delegate() {}
     };
 
     virtual bool StartWatching(PrintServerWatcher::Delegate* delegate) = 0;
     virtual bool StopWatching() = 0;
 
    protected:
     friend class base::RefCountedThreadSafe<PrintServerWatcher>;
     virtual ~PrintServerWatcher();
   };
 
   class PrinterWatcher : public base::RefCountedThreadSafe<PrinterWatcher> {
    public:
     // Callback interface for printer updates notifications.
     class Delegate {
       public:
-        virtual void OnPrinterDeleted() = 0;
-        virtual void OnPrinterChanged() = 0;
-        virtual void OnJobChanged() = 0;
+       virtual void OnPrinterDeleted() = 0;
+       virtual void OnPrinterChanged() = 0;
+       virtual void OnJobChanged() = 0;
 
       protected:
-        virtual ~Delegate() {}
+       virtual ~Delegate() {}
     };
 
     virtual bool StartWatching(PrinterWatcher::Delegate* delegate) = 0;
     virtual bool StopWatching() = 0;
     virtual bool GetCurrentPrinterInfo(
         printing::PrinterBasicInfo* printer_info) = 0;
 
    protected:
     friend class base::RefCountedThreadSafe<PrinterWatcher>;
     virtual ~PrinterWatcher();
@@ skipping 100 matching lines @@
       const base::DictionaryValue* print_system_settings);
 
  protected:
   friend class base::RefCountedThreadSafe<PrintSystem>;
   virtual ~PrintSystem();
 };
 
 }  // namespace cloud_print
 
 #endif  // CHROME_SERVICE_CLOUD_PRINT_PRINT_SYSTEM_H_