Add an about:flag for enabling a reader mode toolbar icon.

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 1610 matching lines @@
     SINGLE_VALUE_TYPE(switches::kManualEnhancedBookmarksOptout)
   },
 #if defined(OS_ANDROID)
   {
     "enable-zero-suggest-experiment",
     IDS_FLAGS_ZERO_SUGGEST_EXPERIMENT_NAME,
     IDS_FLAGS_ZERO_SUGGEST_EXPERIMENT_DESCRIPTION,
     kOsAndroid,
     MULTI_VALUE_TYPE(kZeroSuggestExperimentsChoices)
   },
+  {
+    "enable-reader-mode-toolbar-icon",
+    IDS_FLAGS_READER_MODE_EXPERIMENT_NAME,
+    IDS_FLAGS_READER_MODE_EXPERIMENT_DESCRIPTION,
+    kOsAndroid,
+    SINGLE_VALUE_TYPE(switches::kEnableReaderModeToolbarIcon)
+  },
 #endif
   {
     "num-raster-threads",
     IDS_FLAGS_NUM_RASTER_THREADS_NAME,
     IDS_FLAGS_NUM_RASTER_THREADS_DESCRIPTION,
     kOsAll,
     MULTI_VALUE_TYPE(kNumRasterThreadsChoices)
   },
   {
     "origin-chip-in-omnibox",
@@ skipping 830 matching lines @@
 }
 
 const Experiment* GetExperiments(size_t* count) {
   *count = num_experiments;
   return experiments;
 }
 
 }  // namespace testing
 
 }  // namespace about_flags