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

chrome/browser/previews/previews_infobar_delegate.cc

 // Copyright 2016 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/previews/previews_infobar_delegate.h"
 
 #include "base/feature_list.h"
 #include "base/metrics/field_trial_params.h"
 #include "base/metrics/histogram.h"
 #include "base/optional.h"
@@ skipping 16 matching lines @@
 #include "content/public/browser/render_frame_host.h"
 #include "content/public/browser/web_contents.h"
 #include "ui/base/l10n/l10n_util.h"
 
 #if defined(OS_ANDROID)
 #include "chrome/browser/ui/android/infobars/previews_infobar.h"
 #endif
 
 namespace {
 
+const char kMinStalenessParamName[] = "min_staleness_in_minutes";
+const char kMaxStalenessParamName[] = "max_staleness_in_minutes";
+const int kMinStalenessParamDefaultValue = 2;
+const int kMaxStalenessParamDefaultValue = 1440;
+
 void RecordPreviewsInfoBarAction(
     previews::PreviewsType previews_type,
     PreviewsInfoBarDelegate::PreviewsInfoBarAction action) {
   int32_t max_limit =
       static_cast<int32_t>(PreviewsInfoBarDelegate::INFOBAR_INDEX_BOUNDARY);
   base::LinearHistogram::FactoryGet(
       base::StringPrintf("Previews.InfoBarAction.%s",
                          GetStringNameForType(previews_type).c_str()),
       1, max_limit, max_limit + 1,
       base::HistogramBase::kUmaTargetedHistogramFlag)
@@ skipping 191 matching lines @@
 
 base::string16 PreviewsInfoBarDelegate::GetTimestampText() const {
   if (previews_freshness_.is_null())
     return base::string16();
   if (!base::FeatureList::IsEnabled(
           previews::features::kStalePreviewsTimestamp)) {
     return base::string16();
   }
 
   int min_staleness_in_minutes = base::GetFieldTrialParamByFeatureAsInt(
-      previews::features::kStalePreviewsTimestamp, "min_staleness_in_minutes",
-      0);
+      previews::features::kStalePreviewsTimestamp, kMinStalenessParamName,
+      kMinStalenessParamDefaultValue);
   int max_staleness_in_minutes = base::GetFieldTrialParamByFeatureAsInt(
-      previews::features::kStalePreviewsTimestamp, "max_staleness_in_minutes",
-      0);
+      previews::features::kStalePreviewsTimestamp, kMaxStalenessParamName,
+      kMaxStalenessParamDefaultValue);
 
-  if (min_staleness_in_minutes == 0 || max_staleness_in_minutes == 0)
+  if (min_staleness_in_minutes <= 0 || max_staleness_in_minutes <= 0)
     return base::string16();
 
   base::Time network_time;
   if (g_browser_process->network_time_tracker()->GetNetworkTime(&network_time,
                                                                 nullptr) !=
       network_time::NetworkTimeTracker::NETWORK_TIME_AVAILABLE) {
     // When network time has not been initialized yet, simply rely on the
     // machine's current time.
     network_time = base::Time::Now();
   }
@@ skipping 10 matching lines @@
         IDS_PREVIEWS_INFOBAR_TIMESTAMP_MINUTES,
         base::IntToString16(staleness_in_minutes));
   } else if (staleness_in_minutes < 120) {
     return l10n_util::GetStringUTF16(IDS_PREVIEWS_INFOBAR_TIMESTAMP_ONE_HOUR);
   } else {
     return l10n_util::GetStringFUTF16(
         IDS_PREVIEWS_INFOBAR_TIMESTAMP_HOURS,
         base::IntToString16(staleness_in_minutes / 60));
   }
 }