Add field to monitor last visited time for each search engine

components/search_engines/template_url_data.cc

Index: components/search_engines/template_url_data.cc
diff --git a/components/search_engines/template_url_data.cc b/components/search_engines/template_url_data.cc
index fd04fd3d30f2c6ed73abbe5b4898457477075441..11dbe6001c31367cd3e532c39559bd8b9b27ecd2 100644
--- a/components/search_engines/template_url_data.cc
+++ b/components/search_engines/template_url_data.cc
@@ -15,6 +15,7 @@ TemplateURLData::TemplateURLData()
       id(0),
       date_created(base::Time::Now()),
       last_modified(base::Time::Now()),
+      last_visited(base::Time::Now()),

[Peter Kasting, 2016/11/21 03:35:08]

Seems wrong to set last_visited to Now() (instead of just to Time()) here, as
then we can't distinguish between an engine which was never visited from one
which has been.

(To phrase differently, I think setting this this way causes every newly-created
engine to appear to be "recently visited".)

[ltian, 2016/11/28 22:08:02]

I think it is related to how we define "recently visited"? If we think if a
search engine is detected but is not used for search could also serve as a
visit, then this setting is the right implementation, but if it is not counted
as a visit, then we should set the filed to Time()?

Change it to set as Time() and will also check with Kingston to make sure this
is the right behavior.

       created_by_policy(false),
       usage_count(0),
       prepopulate_id(0),