Add chrome://flag to enable the Stale Previews timestamp

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 aa43d547c4fc76ef8ef63763e4abfdf917e7a548..f111f888e5750ab381396ac73448c2ebbf4457c8 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -1031,6 +1031,15 @@ const FeatureEntry::FeatureVariation kDataReductionMainMenuFeatureVariations[] =
       arraysize(kPersistentMenuItemEnabled), nullptr}};
 #endif  // OS_ANDROID
 
+const FeatureEntry::FeatureParam kStalePreviewsTimestampParams[] = {
+    {"min_staleness_in_minutes", "2"},
+    {"max_staleness_in_minutes", "1440"}};
+
+const FeatureEntry::FeatureVariation
+    kStalePreviewsTimestampFeatureVariations[] = {
+        {"(with staleness params)", kStalePreviewsTimestampParams,
+         arraysize(kStalePreviewsTimestampParams), nullptr}};
+
 const FeatureEntry::Choice kEnableHeapProfilingChoices[] = {
     {flags_ui::kGenericExperimentChoiceDisabled, "", ""},
     {flag_descriptions::kEnableHeapProfilingModePseudo,
@@ -1956,6 +1965,12 @@ const FeatureEntry kFeatureEntries[] = {
      flag_descriptions::kEnableDataReductionProxyLitePageDescription, kOsAll,
      SINGLE_VALUE_TYPE(
          data_reduction_proxy::switches::kEnableDataReductionProxyLitePage)},
+    {"enable-stale-previews-timestamp",
+     flag_descriptions::kEnableStalePreviewsName,
+     flag_descriptions::kEnableStalePreviewsDescription, kOsAll,
+     FEATURE_WITH_PARAMS_VALUE_TYPE(previews::features::kStalePreviewsTimestamp,

[megjablon, 2017/06/21 00:25:07]

Is there any way to add the params for a feature under the Enabled group? It
doesn't make sense for us to have an Enabled group without the params in this
case.

[Alexei Svitkine (slow), 2017/06/22 16:29:21]

Can you simply specify default values for params in the code where you're
querying them?

[megjablon, 2017/06/22 20:43:22]

Done.

+                                    kStalePreviewsTimestampFeatureVariations,
+                                    "StalePreviewsTimestamp")},
     {"enable-data-reduction-proxy-server-experiment",
      flag_descriptions::kEnableDataReductionProxyServerExperimentName,
      flag_descriptions::kEnableDataReductionProxyServerExperimentDescription,