Add a manifest property declaring USB printers supported by an app.

extensions/common/manifest_constants.cc

 // Copyright 2013 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.
 
 #include "extensions/common/manifest_constants.h"
 
 namespace extensions {
 
 namespace manifest_keys {
 
@@ skipping 156 matching lines @@
 const char kTtsVoicesEventTypes[] = "event_types";
 const char kTtsVoicesGender[] = "gender";
 const char kTtsVoicesLang[] = "lang";
 const char kTtsVoicesRemote[] = "remote";
 const char kTtsVoicesVoiceName[] = "voice_name";
 const char kType[] = "type";
 const char kUIOverride[] = "chrome_ui_overrides";
 const char kUpdateURL[] = "update_url";
 const char kUrlHandlers[] = "url_handlers";
 const char kUrlHandlerTitle[] = "title";
+const char kUsbPrinters[] = "usb_printers";
 const char kVersion[] = "version";
 const char kVersionName[] = "version_name";
 const char kWebAccessibleResources[] = "web_accessible_resources";
 const char kWebURLs[] = "app.urls";
 const char kWebview[] = "webview";
 const char kWebviewAccessibleResources[] = "accessible_resources";
 const char kWebviewName[] = "name";
 const char kWebviewPartitions[] = "partitions";
 const char kWhitelist[] = "whitelist";
 
@@ skipping 520 matching lines @@
 const char kWebRequestConflictsWithLazyBackground[] =
     "The 'webRequest' API cannot be used with event pages.";
 #if defined(OS_CHROMEOS)
 const char kIllegalPlugins[] =
     "Extensions cannot install plugins on Chrome OS";
 #endif
 
 }  // namespace manifest_errors
 
 }  // namespace extensions