[Launcher streamlining] Remove RemoveDuplicates

The RemoveDuplicates step of mixing is a noop by design, because every
provider returns different IDs because they use different schemas. This
CL removes it, no user-visible change to results.

Bug: 1028447
Change-Id: I900f371c819cd76ec455c50a44b4e3e395e931c5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2473317Reviewed-by: Thanh Nguyen <thanhdng@chromium.org>
Commit-Queue: Tony Yeoman <tby@chromium.org>
Cr-Commit-Position: refs/heads/master@{#817360}

chrome/browser/ui/app_list/search/mixer.cc

@@ -122,11 +122,6 @@ void Mixer::MixAndPublish(size_t num_max_results, const base::string16& query) {
     results.insert(results.end(), group->results().begin(),
                    group->results().begin() + num_results);
   }
-  // Remove results with duplicate IDs before sorting. If two providers give a
-  // result with the same ID, the result from the provider with the *lower group
-  // number* will be kept (e.g., an app result takes priority over a web store
-  // result with the same ID).
-  RemoveDuplicates(&results);
 
   // Zero state search results: if any search provider won't have any results
   // displayed, but has a high-scoring result that the user hasn't seen many
@@ -144,13 +139,11 @@ void Mixer::MixAndPublish(size_t num_max_results, const base::string16& query) {
   const size_t original_size = results.size();
   if (original_size < num_max_results) {
     // We didn't get enough results. Insert all the results again, and this
-    // time, do not limit the maximum number of results from each group. (This
-    // will result in duplicates, which will be removed by RemoveDuplicates.)
+    // time, do not limit the maximum number of results from each group.
     for (const auto& group : groups_) {
       results.insert(results.end(), group->results().begin(),
                      group->results().end());
     }
-    RemoveDuplicates(&results);
     // Sort just the newly added results. This ensures that, for example, if
     // there are 6 Omnibox results (score = 0.8) and 1 People result (score =
     // 0.4) that the People result will be 5th, not 7th, because the Omnibox
@@ -167,21 +160,6 @@ void Mixer::MixAndPublish(size_t num_max_results, const base::string16& query) {
   model_updater_->PublishSearchResults(new_results);
 }
 
-void Mixer::RemoveDuplicates(SortedResults* results) {
-  SortedResults final;
-  final.reserve(results->size());
-
-  std::set<std::string> id_set;
-  for (const SortData& sort_data : *results) {
-    if (!id_set.insert(sort_data.result->id()).second)
-      continue;
-
-    final.emplace_back(sort_data);
-  }
-
-  results->swap(final);
-}
-
 void Mixer::FetchResults(const base::string16& query) {
   if (search_result_ranker_)
     search_result_ranker_->FetchRankings(query);

chrome/browser/ui/app_list/search/mixer.h

@@ -88,12 +88,6 @@ class Mixer {
   class Group;
   typedef std::vector<std::unique_ptr<Group>> Groups;
 
-  // Removes entries from |results| with duplicate IDs. When two or more results
-  // have the same ID, the earliest one in the |results| list is kept.
-  // NOTE: This is not necessarily the one with the highest *score*, as
-  // |results| may not have been sorted yet.
-  static void RemoveDuplicates(SortedResults* results);
-
   void FetchResults(const base::string16& query);
 
   AppListModelUpdater* const model_updater_;  // Not owned.

chrome/browser/ui/app_list/search/tests/mixer_unittest.cc

@@ -232,28 +232,5 @@ TEST_F(MixerTest, ResultsWithDisplayIndex) {
       GetResults());
 }
 
-TEST_F(MixerTest, RemoveDuplicates) {
-  CreateMixer();
-
-  const std::string dup = "dup";
-
-  // This gives "dup0,dup1,dup2".
-  app_provider()->set_prefix(dup);
-  app_provider()->set_count(3);
-
-  // This gives "dup0,dup1".
-  omnibox_provider()->set_prefix(dup);
-  omnibox_provider()->set_count(2);
-
-  // This gives "dup0".
-  playstore_provider()->set_prefix(dup);
-  playstore_provider()->set_count(1);
-
-  RunQuery();
-
-  // Only three results with unique id are kept.
-  EXPECT_EQ("dup0,dup1,dup2", GetResults());
-}
-
 }  // namespace test
 }  // namespace app_list