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"
 #include "base/time/time.h"
 #include "base/values.h"
 #include "chrome/browser/engagement/site_engagement_metrics.h"
 #include "components/variations/variations_associated_data.h"
 
 namespace {
 
+// The smallest amount by which engagement is incremented. Updated if necessary
+// in SiteEngagementScore::UpdateFromVariations.
+double gMinimumEngagementIncrement = 0.01;
+
 // Delta within which to consider scores equal.
 const double kScoreDelta = 0.001;
 
 // Delta within which to consider internal time values equal. Internal time
 // values are in microseconds, so this delta comes out at one second.
 const double kTimeDelta = 1000000;
 
 // Number of days after the last launch of an origin from an installed shortcut
 // for which WEB_APP_INSTALLED_POINTS will be added to the engagement score.
 const int kMaxDaysSinceShortcutLaunch = 10;
@@ skipping 84 matching lines @@
 }
 
 double SiteEngagementScore::GetMediumEngagementBoundary() {
   return param_values[MEDIUM_ENGAGEMENT_BOUNDARY];
 }
 
 double SiteEngagementScore::GetHighEngagementBoundary() {
   return param_values[HIGH_ENGAGEMENT_BOUNDARY];
 }
 
+double SiteEngagementScore::GetMinimumEngagementIncrement() {
+  return gMinimumEngagementIncrement;
+}
+
 // 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.
     if (param_string.empty() ||
         !base::StringToDouble(param_string, &param_vals[i]) ||
         param_vals[i] < 0) {
       return;
     }
   }
 
   // Once we're sure everything is valid, assign the variation to the param
-  // values array.
-  for (int i = 0; i < MAX_VARIATION; ++i)
+  // values array. Update the minimum engagement increment if it has changed.
+  for (int i = 0; i < MAX_VARIATION; ++i) {
     SiteEngagementScore::param_values[i] = param_vals[i];
+
+    // If the value is one used to increment the site engagement score, update
+    // the minimum engagement increment if necessary.
+    if (i >= POINTS_INCREMENT_FIRST && i <= POINTS_INCREMENT_LAST &&
+        param_vals[i] < gMinimumEngagementIncrement) {
+      gMinimumEngagementIncrement = param_vals[i];
+    }
+  }
 }
 
 SiteEngagementScore::SiteEngagementScore(base::Clock* clock,
                            const base::DictionaryValue& score_dict)
     : SiteEngagementScore(clock) {
   score_dict.GetDouble(kRawScoreKey, &raw_score_);
   score_dict.GetDouble(kPointsAddedTodayKey, &points_added_today_);
 
   double internal_time;
   if (score_dict.GetDouble(kLastEngagementTimeKey, &internal_time))
@@ skipping 143 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;
 }