Generalize Previews Type code

components/previews/core/previews_experiments.h

 // Copyright 2016 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 COMPONENTS_PREVIEWS_CORE_PREVIEWS_EXPERIMENTS_H_
 #define COMPONENTS_PREVIEWS_CORE_PREVIEWS_EXPERIMENTS_H_
 
 #include "base/time/time.h"
 
 namespace previews {
 
 namespace params {
 
 // The maximum number of recent previews navigations the black list looks at to
 // determine if a host is blacklisted.
 size_t MaxStoredHistoryLengthForBlackList();
 
 // The maximum number of hosts allowed in the in memory black list.
 size_t MaxInMemoryHostsInBlackList();
 
 // The number of recent navigations that were opted out of that would trigger
 // the host to be blacklisted.
 int BlackListOptOutThreshold();
 
 // The amount of time a host remains blacklisted due to opt outs.
 base::TimeDelta BlackListDuration();
 
 }  // namespace params
 
+enum class PreviewsType {
+  NONE = 0,
+  OFFLINE = 1,
+  LAST = 2,
+};
+
 // Returns true if any client-side previews experiment is active.
 bool IsIncludedInClientSidePreviewsExperimentsFieldTrial();
 
-// Returns true if the field trial that should enable offline pages for
+// Returns true if the field trial that should enable previews for |type| for
 // prohibitvely slow networks is active.
-bool IsOfflinePreviewsEnabled();
+bool IsPreviewsTypeEnabled(PreviewsType type);
 
 // Sets the appropriate state for field trial and variations to imitate the
 // offline pages field trial.
 bool EnableOfflinePreviewsForTesting();
 
 }  // namespace previews
 
 #endif  // COMPONENTS_PREVIEWS_CORE_PREVIEWS_EXPERIMENTS_H_