Add an about:flag to support alternative data saver features

chrome/browser/flag_descriptions.cc

Index: chrome/browser/flag_descriptions.cc
diff --git a/chrome/browser/flag_descriptions.cc b/chrome/browser/flag_descriptions.cc
index a05be8ee7f43a031a9f406ff54c3e219e09e8529..9401e5af69831ae7a00a4bc18710cb836f53f475 100644
--- a/chrome/browser/flag_descriptions.cc
+++ b/chrome/browser/flag_descriptions.cc
@@ -1162,6 +1162,16 @@ const char kEnableDataReductionProxyLitePageDescription[] =
     "shown instead of image placeholders when Lo-Fi is on. Data Saver and "
     "Lo-Fi must be enabled for lite pages to be shown.";
 
+const char kDataReductionProxyServerAlternative[] =
+    "Use alternative server configuration";
+
+const char kEnableDataReductionProxyServerExperimentName[] =
+    "Use an alternative Data Saver back end configuration.";
+
+const char kEnableDataReductionProxyServerExperimentDescription[] =
+    "Enable a different approach to saving data by configuring the back end "
+    "server";
+
 const char kDataReductionProxyCarrierTestName[] =
     "Enable a carrier-specific Data Reduction Proxy for testing.";