Include USB printers in printer list as "provisional" devices.

chrome/chrome_browser_ui.gypi

 # Copyright 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.
 
 {
   'variables': {
     # There are two sections of sources:
     # * "Platform"-based sources (OS, toolkit, etc.)
     # * Feature/directory-based sources (e.g., history, printing)
 
@@ skipping 2671 matching lines @@
       'browser/ui/webui/policy_ui.cc',
       'browser/ui/webui/policy_ui.h',
     ],
     'chrome_browser_ui_print_preview_sources': [
       'browser/ui/webui/print_preview/extension_printer_handler.cc',
       'browser/ui/webui/print_preview/extension_printer_handler.h',
       'browser/ui/webui/print_preview/print_preview_handler.cc',
       'browser/ui/webui/print_preview/print_preview_handler.h',
       'browser/ui/webui/print_preview/print_preview_ui.cc',
       'browser/ui/webui/print_preview/print_preview_ui.h',
-      'browser/ui/webui/print_preview/printer_handler.cc',
       'browser/ui/webui/print_preview/printer_handler.h',
       'browser/ui/webui/print_preview/sticky_settings.cc',
       'browser/ui/webui/print_preview/sticky_settings.h',
     ],
     # For when enable_service_discovery is set.
     'chrome_browser_ui_service_discovery_sources': [
       'browser/ui/webui/local_discovery/local_discovery_ui.cc',
       'browser/ui/webui/local_discovery/local_discovery_ui.h',
       'browser/ui/webui/local_discovery/local_discovery_ui_handler.cc',
       'browser/ui/webui/local_discovery/local_discovery_ui_handler.h',
@@ skipping 482 matching lines @@
           ],
           'sources': [
             '<@(chrome_browser_ui_non_mobile_sources)',
             '<@(chrome_browser_ui_omnibox_non_mobile_sources)',
           ],
         }],
       ],
     },
   ],
 }