Revert of Moving previews code from components/ to chrome/

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 <memory>
 #include <utility>
 #include <vector>
@@ skipping 34 matching lines @@
 base::TimeDelta SingleOptOutDuration();
 
 // The amount of time that an offline page is considered fresh enough to be
 // shown as a preview.
 base::TimeDelta OfflinePreviewFreshnessDuration();
 
 // The threshold of EffectiveConnectionType above which previews should not be
 // served.
 net::EffectiveConnectionType EffectiveConnectionTypeThreshold();
 
-// Whether offline previews are enabled.
-bool IsOfflinePreviewsEnabled();
-
-// The blacklist version for offline previews.
-int OfflinePreviewsVersion();
-
 }  // namespace params
 
 enum class PreviewsType {
   NONE = 0,
-  // The user is shown an offline page as a preview.
   OFFLINE = 1,
   // Insert new enum values here. Keep values sequential to allow looping
   // from NONE+1 to LAST-1.
   LAST = 2,
 };
 
 typedef std::vector<std::pair<PreviewsType, int>> PreviewsTypeList;
 
 // Returns true if any client-side previews experiment is active.
 bool IsIncludedInClientSidePreviewsExperimentsFieldTrial();
 
+// Returns true if the field trial that should enable previews for |type| for
+// prohibitvely slow networks is active.
+bool IsPreviewsTypeEnabled(PreviewsType type);
+
+// Returns the version of preview treatment |type|. Defaults to 0 if not
+// specified in field trial config.
+int GetPreviewsTypeVersion(PreviewsType type);
+
+// Returns the enabled PreviewsTypes with their version.
+std::unique_ptr<PreviewsTypeList> GetEnabledPreviews();
+
 // 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_