Add support to previews/ for Server LoFi and LitePages

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 <string>
 #include <utility>
 #include <vector>
 
 #include "base/time/time.h"
 #include "net/nqe/effective_connection_type.h"
 
 namespace previews {
 
 namespace params {
 
@@ skipping 53 matching lines @@
 
 enum class PreviewsType {
   NONE = 0,
 
   // The user is shown an offline page as a preview.
   OFFLINE = 1,
 
   // Replace images with placeholders generated on the client.
   CLIENT_LOFI = 2,
 
+  // The user is shown a server lite page.
+  LITE_PAGE = 3,
+
+  // The user is shown a server LoFi page.
+  SERVER_LOFI = 4,
+
   // Insert new enum values here. Keep values sequential to allow looping
   // from NONE+1 to LAST-1.
-  LAST = 3,
+  LAST = 5,
 };
 
 typedef std::vector<std::pair<PreviewsType, int>> PreviewsTypeList;
 
 // Returns true if any client-side previews experiment is active.
 bool IsIncludedInClientSidePreviewsExperimentsFieldTrial();
 
+// Gets the string representation of |type|.
+std::string GetStringNameForType(PreviewsType type);
+
 }  // namespace previews
 
 #endif  // COMPONENTS_PREVIEWS_CORE_PREVIEWS_EXPERIMENTS_H_