Add an about:flag to support alternative data saver features

chrome/browser/about_flags.cc

 // Copyright (c) 2012 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 "chrome/browser/about_flags.h"
 
 #include <iterator>
 #include <map>
 #include <set>
 #include <utility>
@@ skipping 1874 matching lines @@
 #endif  // OS_MACOSX
     {"data-reduction-proxy-lo-fi",
      flag_descriptions::kDataReductionProxyLoFiName,
      flag_descriptions::kDataReductionProxyLoFiDescription, kOsAll,
      MULTI_VALUE_TYPE(kDataReductionProxyLoFiChoices)},
     {"enable-data-reduction-proxy-lite-page",
      flag_descriptions::kEnableDataReductionProxyLitePageName,
      flag_descriptions::kEnableDataReductionProxyLitePageDescription, kOsAll,
      SINGLE_VALUE_TYPE(
          data_reduction_proxy::switches::kEnableDataReductionProxyLitePage)},
+    {"enable-data-reduction-proxy-alternative-back-end",

[tbansal1, 2017/05/19 16:27:23]

I still think this should be a dropdown flag (with two options: Default and
Alternative). The flag should map to the existing switch for setting the server
experiments.

Right now, we have two different switches which do exactly the same thing.
Having a single switch would reduce the confusion. Also, see:
https://bugs.chromium.org/p/chromium/issues/detail?id=656195#c1

[RyanSturm, 2017/05/23 22:04:57]

Done.

+     flag_descriptions::kEnableDataReductionProxyAlternativeBackEndName,
+     flag_descriptions::kEnableDataReductionProxyAlternativeBackEndDescription,
+     kOsAll,
+     FEATURE_VALUE_TYPE(data_reduction_proxy::features::
+                            kDataReductionProxyAlternativeBackEnd)},
 #if defined(OS_ANDROID)
     {"enable-data-reduction-proxy-savings-promo",
      flag_descriptions::kEnableDataReductionProxySavingsPromoName,
      flag_descriptions::kEnableDataReductionProxySavingsPromoDescription,
      kOsAndroid,
      SINGLE_VALUE_TYPE(data_reduction_proxy::switches::
                            kEnableDataReductionProxySavingsPromo)},
     {"enable-data-reduction-proxy-main-menu",
      flag_descriptions::kEnableDataReductionProxyMainMenuName,
      flag_descriptions::kEnableDataReductionProxyMainMenuDescription,
@@ skipping 1263 matching lines @@
 const base::HistogramBase::Sample kBadSwitchFormatHistogramId = 0;
 
 const FeatureEntry* GetFeatureEntries(size_t* count) {
   *count = arraysize(kFeatureEntries);
   return kFeatureEntries;
 }
 
 }  // namespace testing
 
 }  // namespace about_flags