Implement an observer interface for the site engagement service.

chrome/browser/engagement/site_engagement_score.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/engagement/site_engagement_score.h"
 
 #include <cmath>
 
 #include "base/strings/string_number_conversions.h"
 #include "base/time/clock.h"
@@ skipping 101 matching lines @@
 }
 
 double SiteEngagementScore::GetMediumEngagementBoundary() {
   return param_values[MEDIUM_ENGAGEMENT_BOUNDARY];
 }
 
 double SiteEngagementScore::GetHighEngagementBoundary() {
   return param_values[HIGH_ENGAGEMENT_BOUNDARY];
 }
 
+double SiteEngagementScore::GetMinimumEngagementIncrement() {
+  return GetHiddenMediaPoints();

[calamity, 2016/05/19 03:28:22]

This will limit the way we modify the experimental numbers right? Can we
calculate this as a static when we update from variations?

[dominickn, 2016/05/19 04:36:14]

Done.

+}
+
 // static
 void SiteEngagementScore::UpdateFromVariations(const char* param_name) {
   double param_vals[MAX_VARIATION];
 
   for (int i = 0; i < MAX_VARIATION; ++i) {
     std::string param_string =
         variations::GetVariationParamValue(param_name, kVariationNames[i]);
 
     // Bail out if we didn't get a param string for the key, or if we couldn't
     // convert the param string to a double, or if we get a negative value.
@@ skipping 164 matching lines @@
   param_values[HIDDEN_MEDIA_POINTS] = 0.01;
   param_values[WEB_APP_INSTALLED_POINTS] = 5;
   param_values[BOOTSTRAP_POINTS] = 8;
   param_values[MEDIUM_ENGAGEMENT_BOUNDARY] = 5;
   param_values[HIGH_ENGAGEMENT_BOUNDARY] = 50;
 
   // This is set to zero to avoid interference with tests and is set when
   // testing this functionality.
   param_values[FIRST_DAILY_ENGAGEMENT] = 0;
 }