Implement an observer interface for the site engagement service.

chrome/browser/engagement/site_engagement_score.h

Index: chrome/browser/engagement/site_engagement_score.h
diff --git a/chrome/browser/engagement/site_engagement_score.h b/chrome/browser/engagement/site_engagement_score.h
index 7bebca721288261319567a1b77d8b93ecc64c414..a127cbd641dc31c8203d02a0549f231568b71032 100644
--- a/chrome/browser/engagement/site_engagement_score.h
+++ b/chrome/browser/engagement/site_engagement_score.h
@@ -30,6 +30,7 @@ class SiteEngagementScore {
 
     // The number of points given for navigations.
     NAVIGATION_POINTS,
+    POINTS_INCREMENT_FIRST = NAVIGATION_POINTS,
 
     // The number of points given for user input.
     USER_INPUT_POINTS,
@@ -39,6 +40,7 @@ class SiteEngagementScore {
     // site to reach the daily engagement maximum.
     VISIBLE_MEDIA_POINTS,
     HIDDEN_MEDIA_POINTS,
+    POINTS_INCREMENT_LAST = HIDDEN_MEDIA_POINTS,

[calamity, 2016/05/24 08:09:32]

This won't work if we add a new increment type to the bottom of this enum. We
need either a function or a new enum that tells us exactly what the increment
types are.

[dominickn, 2016/05/25 07:21:32]

Is there any reason to keep this enum append only? Even if we change Finch
configs, there is a mechanism to target experiments to certain versions so that
shouldn't be an issue. I've added a comment to make this more explicit.
Otherwise, the increment stuff isn't really necessary in this CL - I kept it
because it seems like we were missing the complement function for
GetEngagementLevel.

[calamity, 2016/05/31 05:56:35]

Guess not. This whole 3-way mapping is getting a bit messy though =S

 
     // The number of points added to engagement when a site is launched from
     // homescreen or added as a bookmark app. This bonus will apply for ten days
@@ -76,6 +78,7 @@ class SiteEngagementScore {
   static double GetBootstrapPoints();
   static double GetMediumEngagementBoundary();
   static double GetHighEngagementBoundary();
+  static double GetMinimumEngagementIncrement();
 
   // Update the default engagement settings via variations.
   static void UpdateFromVariations(const char* param_name);