Add a "guard" content settings type for chooser permissions.

components/content_settings/core/common/content_settings.cc

 // Copyright (c) 2011 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 "components/content_settings/core/common/content_settings.h"
 
 #include "base/containers/hash_tables.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/stl_util.h"
@@ skipping 33 matching lines @@
     CONTENT_SETTINGS_TYPE_SSL_CERT_DECISIONS,
     CONTENT_SETTINGS_TYPE_DEFAULT,  // METRO_SWITCH_TO_DESKTOP (deprecated).
 #if defined(OS_ANDROID) || defined(OS_CHROMEOS)
     CONTENT_SETTINGS_TYPE_PROTECTED_MEDIA_IDENTIFIER,
 #else
     CONTENT_SETTINGS_TYPE_DEFAULT,  // PROTECTED_MEDIA_IDENTIFIER (mobile only).
 #endif
     CONTENT_SETTINGS_TYPE_APP_BANNER,
     CONTENT_SETTINGS_TYPE_SITE_ENGAGEMENT,
     CONTENT_SETTINGS_TYPE_DURABLE_STORAGE,
+    CONTENT_SETTINGS_TYPE_USB,
 };
 
 int ContentSettingTypeToHistogramValue(ContentSettingsType content_setting,
                                        size_t* num_values) {
   // Translate the list above into a map for fast lookup.
   typedef base::hash_map<int, int> Map;
   CR_DEFINE_STATIC_LOCAL(Map, kMap, ());
   if (kMap.empty()) {
     for (size_t i = 0; i < arraysize(kHistogramOrder); ++i) {
       if (kHistogramOrder[i] != CONTENT_SETTINGS_TYPE_DEFAULT)
@@ skipping 18 matching lines @@
       source(source),
       incognito(incognito) {}
 
 ContentSettingPatternSource::ContentSettingPatternSource()
     : setting(CONTENT_SETTING_DEFAULT), incognito(false) {
 }
 
 RendererContentSettingRules::RendererContentSettingRules() {}
 
 RendererContentSettingRules::~RendererContentSettingRules() {}