Initial CL for Data Saver (Flywheel) prompt when cellular network detected

chrome/browser/about_flags.cc

Index: chrome/browser/about_flags.cc
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index 7f41b7f2bcae79c6519c8e376d453503e43fae94..100929bf1a60633d310ca6c4fd296bd697ad933e 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -2185,6 +2185,15 @@ const Experiment kExperiments[] = {
         switches::kSyncServiceURL,
         "https://chrome-sync.sandbox.google.com/chrome-sync/alpha")
   },
+#if defined(OS_CHROMEOS)
+  {
+    "enable-datasaver-prompt",
+    IDS_FLAGS_ENABLE_DATASAVER_PROMPT_NAME,
+    IDS_FLAGS_ENABLE_DATASAVER_PROMPT_DESCRIPTION,
+    kOsCrOS,
+    SINGLE_VALUE_TYPE(chromeos::switches::kEnableDataSaverPrompt)
+  },
+#endif  // defined(OS_CHROMEOS)
 
   // NOTE: Adding new command-line switches requires adding corresponding
   // entries to enum "LoginCustomFlags" in histograms.xml. See note in