Fix duplicate search results in launcher

There are some edge cases where we still show duplicate results. Until
we remove the old logic that does this, we should continue de-duping.

Bug: 1156846
Change-Id: I4366467ebf645c3b957bea6916be90be71bbcdc3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2596456
Commit-Queue: Tony Yeoman <tby@chromium.org>
Reviewed-by: Thanh Nguyen <thanhdng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#837929}

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

@@ -15,6 +15,8 @@
 #include "base/macros.h"
 #include "base/metrics/field_trial_params.h"
 #include "base/numerics/ranges.h"
+#include "base/strings/strcat.h"
+#include "base/strings/string_number_conversions.h"
 #include "chrome/browser/ui/app_list/app_list_model_updater.h"
 #include "chrome/browser/ui/app_list/search/chrome_search_result.h"
 #include "chrome/browser/ui/app_list/search/search_controller.h"
@@ -24,6 +26,32 @@
 #include "chrome/browser/ui/app_list/search/search_result_ranker/search_result_ranker.h"
 
 namespace app_list {
+namespace {
+
+// TODO(crbug.com/1028447): This is a stop-gap until we remove the two-stage
+// result adding logic in Mixer::MixAndPublish. Remove this when possible.
+void RemoveDuplicates(Mixer::SortedResults* results) {
+  Mixer::SortedResults deduplicated;
+  deduplicated.reserve(results->size());
+
+  std::set<std::string> seen;
+  for (const Mixer::SortData& sort_data : *results) {
+    // If a result is intended for display in two views, we will have two
+    // results with the same id but different display types. We want to keep
+    // both of these, so insert concat(id, display_type).
+    const std::string display_type = base::NumberToString(
+        static_cast<int>(sort_data.result->display_type()));
+    if (!seen.insert(base::StrCat({sort_data.result->id(), display_type}))
+             .second)
+      continue;
+
+    deduplicated.emplace_back(sort_data);
+  }
+
+  results->swap(deduplicated);
+}
+
+}  // namespace
 
 Mixer::SortData::SortData() : result(nullptr), score(0.0) {}
 
@@ -151,6 +179,7 @@ void Mixer::MixAndPublish(size_t num_max_results, const base::string16& query) {
     // would not be seen at all once the result list is truncated.)
     std::sort(results.begin() + original_size, results.end());
   }
+  RemoveDuplicates(&results);
 
   std::vector<ChromeSearchResult*> new_results;
   for (const SortData& sort_data : results) {