[Android] Sort custom search engines based on last visited time and display only top 3 most recentl…

components/search_engines/template_url_service.h

Index: components/search_engines/template_url_service.h
diff --git a/components/search_engines/template_url_service.h b/components/search_engines/template_url_service.h
index b387f7bef8f1d5ac6cf201e83d1c83e47ffe7036..eaa6e47e75a0f3e91bfe7e78031422096a2ebaf7 100644
--- a/components/search_engines/template_url_service.h
+++ b/components/search_engines/template_url_service.h
@@ -137,10 +137,11 @@ class TemplateURLService : public WebDataServiceConsumer,
   // prepopulate list or created by policy.
   bool IsPrepopulatedOrCreatedByPolicy(const TemplateURL* template_url);
 
-  // Returns whether |template_url| is the current default or return true for
-  // IsPrepopulatedOrCreatedByPolicy(). This is meant to highlight the current,
-  // default, as well as the other most likely choices of default engine,
-  // separately from a full list of all TemplateURLs (which might be very long).
+  // Returns whether |template_url| should be shown in the list of engines
+  // most likely to be selected as a default engine. This is meant to highlight
+  // the current default, as well as the other most likely choices of default
+  // engine, separately from a full list of all TemplateURLs (which might be
+  // very long).
   bool ShowInDefaultList(const TemplateURL* template_url);
 
   // Adds to |matches| all TemplateURLs whose keywords begin with |prefix|,
@@ -377,6 +378,9 @@ class TemplateURLService : public WebDataServiceConsumer,
   static syncer::SyncData CreateSyncDataFromTemplateURL(
       const TemplateURL& turl);
 
+  // Updates the last_visited time of |url| to the current time.
+  void UpdateTemplateURLVisitTime(TemplateURL* url);

[Peter Kasting, 2016/12/16 08:37:18]

Nit: If you're going to move this, you need to move the definition to match. 
.cc and .h files must stay in the same order.

Consider also where in this list this should go; try to group related things. 
In this case, you've inserted your method right between two "create XXX" static
methods for sync that are closely related to each other, which doesn't make
sense.

Looking at how you use these, it's merely being exposed to a test-only function
on TemplateUrlServiceAndroid, which is almost an implementation-detail class. 
It probably makes sense to leave it where it was and expose via a friend
declaration instead, since we don't really want anyone else calling this method.

+
   // Creates a new heap-allocated TemplateURL* which is populated by overlaying
   // |sync_data| atop |existing_turl|.  |existing_turl| may be NULL; if not it
   // remains unmodified.  The caller owns the returned TemplateURL*.
@@ -569,9 +573,6 @@ class TemplateURLService : public WebDataServiceConsumer,
   // SetKeywordSearchTermsForURL is invoked.
   void UpdateKeywordSearchTermsForURL(const URLVisitedDetails& details);
 
-  // Updates the last_visited time of |url| to the current time.
-  void UpdateTemplateURLVisitTime(TemplateURL* url);
-
   // If necessary, generates a visit for the site http:// + t_url.keyword().
   void AddTabToSearchVisit(const TemplateURL& t_url);