Make app list search result mixer more resilient to reordering.

chrome/browser/ui/app_list/search/mixer_unittest.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 <string>
 
 #include "base/memory/scoped_vector.h"
 #include "base/strings/string16.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
@@ skipping 232 matching lines @@
 
   // The second result will still use the original object, but have a different
   // title, since the ID did not change.
   EXPECT_EQ(old_ui_result_ids[1],
             TestSearchResult::GetInstanceId(ui_results.GetItemAt(1)));
   EXPECT_EQ(kNewAppTitle, ui_results.GetItemAt(1)->title());
 
   // The third result will use the original object as the ID did not change.
   EXPECT_EQ(old_ui_result_ids[2],
             TestSearchResult::GetInstanceId(ui_results.GetItemAt(2)));
+
+  // Save the current |ui_results| order which should is app4, app2, app3.
+  old_ui_result_ids.clear();
+  for (size_t i = 0; i < ui_results.item_count(); ++i) {
+    old_ui_result_ids.push_back(
+        TestSearchResult::GetInstanceId(ui_results.GetItemAt(i)));
+  }
+
+  // Reorder the existing results and add a new one in the second place.
+  new_results[0] = Mixer::SortData(result2.get(), 1.0f);
+  new_results[1] = Mixer::SortData(result1.get(), 1.0f);

[Matt Giuca, 2014/07/09 01:30:54]

I think this is the "new one", correct? (Because result1 was not used in the
previous test, so it is "new".) I think it's kind of unclear... a casual reading
of this is like "huh? you added a new one in the fourth place, not the second!"

I think you should add a result5 and use that in place of result1 here, so it's
clear that it is a totally new result.

[calamity, 2014/07/09 03:03:48]

Done.

+  new_results[2] = Mixer::SortData(result3.get(), 1.0f);
+  new_results.push_back(Mixer::SortData(result4.get(), 1.0f));
+
+  Mixer::Publish(new_results, &ui_results);
+  EXPECT_EQ(4u, ui_results.item_count());
+
+  // The reordered results should use the original objects.
+  EXPECT_EQ(old_ui_result_ids[0],
+            TestSearchResult::GetInstanceId(ui_results.GetItemAt(3)));
+  EXPECT_EQ(old_ui_result_ids[1],
+            TestSearchResult::GetInstanceId(ui_results.GetItemAt(0)));
+  EXPECT_EQ(old_ui_result_ids[2],
+            TestSearchResult::GetInstanceId(ui_results.GetItemAt(2)));
 }
 
 }  // namespace test
 }  // namespace app_list