Use the max use count on autofill profile merge.

components/autofill/core/browser/autofill_profile.cc

 // Copyright 2013 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 "components/autofill/core/browser/autofill_profile.h"
 
 #include <algorithm>
 #include <functional>
 #include <map>
 #include <memory>
@@ skipping 446 matching lines @@
       !comparator.MergeEmailAddresses(profile, *this, &email) ||
       !comparator.MergeCompanyNames(profile, *this, &company) ||
       !comparator.MergePhoneNumbers(profile, *this, &phone_number) ||
       !comparator.MergeAddresses(profile, *this, &address)) {
     NOTREACHED();
     return false;
   }
 
   set_origin(profile.origin());
   set_language_code(profile.language_code());
-  set_use_count(profile.use_count() + use_count());
-  if (profile.use_date() > use_date())
-    set_use_date(profile.use_date());
+  set_use_count(std::max(profile.use_count(), use_count()));

[Mathieu, 2016/07/21 19:16:01]

Let's add the rationale for the future reader!

[Roger McFarlane (Chromium), 2016/07/22 01:15:25]

Done.

+  set_use_date(std::max(profile.use_date(), use_date()));
 
   // Now that the preferred values have been obtained, update the fields which
   // need to be modified, if any. Note: that we're comparing the fields for
   // representational equality below (i.e., are the values byte for byte the
   // same).
 
   bool modified = false;
 
   if (name_ != name) {
     name_ = name;
@@ skipping 366 matching lines @@
             << " " << UTF16ToUTF8(profile.GetRawInfo(ADDRESS_HOME_CITY)) << " "
             << UTF16ToUTF8(profile.GetRawInfo(ADDRESS_HOME_STATE)) << " "
             << UTF16ToUTF8(profile.GetRawInfo(ADDRESS_HOME_ZIP)) << " "
             << UTF16ToUTF8(profile.GetRawInfo(ADDRESS_HOME_SORTING_CODE)) << " "
             << UTF16ToUTF8(profile.GetRawInfo(ADDRESS_HOME_COUNTRY)) << " "
             << profile.language_code() << " "
             << UTF16ToUTF8(profile.GetRawInfo(PHONE_HOME_WHOLE_NUMBER));
 }
 
 }  // namespace autofill