Allow the minimum time between banner trigger visits to be varied via field trials.

chrome/browser/banners/app_banner_settings_helper.h

 // Copyright 2014 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.
 
 #ifndef CHROME_BROWSER_BANNERS_APP_BANNER_SETTINGS_HELPER_H_
 #define CHROME_BROWSER_BANNERS_APP_BANNER_SETTINGS_HELPER_H_
 
 #include <set>
 #include <string>
 #include <vector>
@@ skipping 104 matching lines @@
       content::WebContents* web_contents,
       const GURL& origin_url,
       const std::string& package_name_or_start_url,
       AppBannerEvent event);
 
   // Set the engagement weights assigned to direct and indirect navigations.
   // This is only exposed for testing.
   static void SetEngagementWeights(double direct_engagement,
                                    double indirect_engagement);
 
+  // Set the minimum number of minutes between banner visits that will
+  // trigger a could show banner event. This must be less than the
+  // number of minutes in a day, and evenly divide the number of minutes
+  // in a day.
+  static void SetMinimumMinutesBetweenVisits(unsigned int minutes);
+
+  // Bucket a given time to the given resolution in local time.
+  static base::Time BucketTimeToResolution(base::Time time,
+                                           unsigned int minutes);
+
+  // Queries a field trial for updates to the default number of minutes between
+  // site visits counted for the purposes of displaying a banner.
+  static void UpdateMinutesBetweenVisits();
+
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(AppBannerSettingsHelper);
 };
 
 #endif  // CHROME_BROWSER_BANNERS_APP_BANNER_SETTINGS_HELPER_H_