Use service process to collect printers.

chrome/browser/extensions/api/cloud_print_private/cloud_print_private_api.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_EXTENSIONS_API_CLOUD_PRINT_PRIVATE_CLOUD_PRINT_PRIVATE_API_H_
 #define CHROME_BROWSER_EXTENSIONS_API_CLOUD_PRINT_PRIVATE_CLOUD_PRINT_PRIVATE_API_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 69 matching lines @@
     : public ChromeAsyncExtensionFunction {
  public:
   DECLARE_EXTENSION_FUNCTION("cloudPrintPrivate.getPrinters",
                              CLOUDPRINTPRIVATE_GETPRINTERS)
 
   CloudPrintPrivateGetPrintersFunction();
 
  protected:
   virtual ~CloudPrintPrivateGetPrintersFunction();
 
-  void CollectPrinters();
+ private:
+  void SendResults(const std::vector<std::string>& printers);
 
   // ExtensionFunction:
   virtual bool RunImpl() OVERRIDE;
 };
 
 class CloudPrintPrivateGetClientIdFunction
     : public ChromeAsyncExtensionFunction {
  public:
   DECLARE_EXTENSION_FUNCTION("cloudPrintPrivate.getClientId",
                              CLOUDPRINTPRIVATE_GETCLIENTID);
 
   CloudPrintPrivateGetClientIdFunction();
 
  protected:
   virtual ~CloudPrintPrivateGetClientIdFunction();
 
   // ExtensionFunction:
   virtual bool RunImpl() OVERRIDE;
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_CLOUD_PRINT_PRIVATE_CLOUD_PRINT_PRIVATE_API_H_