Add title update merge logic to reading list entry

components/reading_list/ios/reading_list_store_unittest.mm

 // 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 "components/reading_list/ios/reading_list_store.h"
 
 #include <map>
 #include <set>
 
 #include "base/bind.h"
@@ skipping 313 matching lines @@
   entryA.set_title("Foo Bar");
   entryB.set_title("Foo Bar");
   entryA.set_status(sync_pb::ReadingListSpecifics::UNREAD);
   entryB.set_status(sync_pb::ReadingListSpecifics::UNREAD);
   entryA.set_creation_time_us(10);
   entryB.set_creation_time_us(10);
   entryA.set_first_read_time_us(50);
   entryB.set_first_read_time_us(50);
   entryA.set_update_time_us(100);
   entryB.set_update_time_us(100);
+  entryA.set_update_title_time_us(110);
+  entryB.set_update_title_time_us(110);
   // Equal entries can be submitted.
   ExpectAB(entryA, entryB, true);
   ExpectAB(entryB, entryA, true);
 
   // Try to update each field.
 
   // You cannot change the URL of an entry.
   entryA.set_url("http://foo.foo/");
   EXPECT_FALSE(ReadingListStore::CompareEntriesForSync(entryA, entryB));
   EXPECT_FALSE(ReadingListStore::CompareEntriesForSync(entryB, entryA));
   entryA.set_url("http://foo.bar/");
 
-  // You can set a title to a title later in alphabetical order.
+  // You can set a title to a title later in alphabetical order if the
+  // update_title_time is the same. If a title has been more recently updated,
+  // the only possible transition is to this one.
   entryA.set_title("");
   ExpectAB(entryA, entryB, true);
   ExpectAB(entryB, entryA, false);
+  entryA.set_update_title_time_us(109);
+  ExpectAB(entryA, entryB, true);
+  ExpectAB(entryB, entryA, false);
+  entryA.set_update_title_time_us(110);
+

[pavely, 2017/01/04 00:12:32]

I think set_update_title_time_us is logically related to corresponding call to
set_title. I would put empty line before set_update_title_time_us, not after it.
The same applies to two more places below.

[gambard, 2017/01/04 09:57:02]

set_update_title_time_us(110); reset the value of the update_title_time_us to
its default value. This is why it is the last line of the paragraph.

   entryA.set_title("Foo Aar");
   ExpectAB(entryA, entryB, true);
   ExpectAB(entryB, entryA, false);
+  entryA.set_update_title_time_us(109);
+  ExpectAB(entryA, entryB, true);
+  ExpectAB(entryB, entryA, false);
+  entryA.set_update_title_time_us(110);
+
   entryA.set_title("Foo Ba");
   ExpectAB(entryA, entryB, true);
   ExpectAB(entryB, entryA, false);
+  entryA.set_update_title_time_us(109);
+  ExpectAB(entryA, entryB, true);
+  ExpectAB(entryB, entryA, false);
+  entryA.set_update_title_time_us(110);
+
+  entryA.set_title("Foo Bas");
+  ExpectAB(entryA, entryB, false);
+  ExpectAB(entryB, entryA, true);
+  entryA.set_update_title_time_us(109);
+  ExpectAB(entryA, entryB, true);
+  ExpectAB(entryB, entryA, false);
+  entryA.set_update_title_time_us(110);
   entryA.set_title("Foo Bar");
 
+  // Update times.
   entryA.set_creation_time_us(9);
   ExpectAB(entryA, entryB, true);
   ExpectAB(entryB, entryA, false);
   entryA.set_first_read_time_us(51);
   ExpectAB(entryA, entryB, true);
   ExpectAB(entryB, entryA, false);
   entryA.set_first_read_time_us(49);
   ExpectAB(entryA, entryB, true);
   ExpectAB(entryB, entryA, false);
   entryA.set_first_read_time_us(0);
@@ skipping 34 matching lines @@
     entryB.set_status(status_oder[index_a]);
     ExpectAB(entryA, entryB, true);
     ExpectAB(entryB, entryA, true);
     for (int index_b = index_a + 1; index_b < 3; index_b++) {
       entryB.set_status(status_oder[index_b]);
       ExpectAB(entryA, entryB, true);
       ExpectAB(entryB, entryA, false);
     }
   }
 }