[Launcher settings] Splits max requested and max shown results.

We request a certain number of results from the settings search backend,
and also have a maximum number of results we want to show. However the
backend can return duplicate results that are removed, so we should
request a few more results than we need to display.

This CL also removes a TODO on testing the new settings results.

Bug: 1068851
Change-Id: I7a80766112f06679ceae19057f6e9adfe36c44aa
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2217721Reviewed-by: Rachel Wong <wrong@chromium.org>
Commit-Queue: Tony Yeoman <tby@chromium.org>
Cr-Commit-Position: refs/heads/master@{#773006}

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

@@ -33,7 +33,8 @@ using SearchResultPtr = chromeos::settings::mojom::SearchResultPtr;
 
 constexpr char kOsSettingsResultPrefix[] = "os-settings://";
 constexpr float kScoreEps = 1e-5;
-constexpr size_t kMaxResults = 2u;
+constexpr size_t kNumRequestedResults = 5u;
+constexpr size_t kMaxShownResults = 2u;
 
 // Various error states of the OsSettingsProvider. kOk is currently not emitted,
 // but may be used in future. These values persist to logs. Entries should not
@@ -152,11 +153,7 @@ void OsSettingsProvider::Start(const base::string16& query) {
 
   // Invalidate weak pointers to cancel existing searches.
   weak_factory_.InvalidateWeakPtrs();
-  // TODO(crbug.com/1068851): There are currently only a handful of settings
-  // returned from the backend. Once the search service has finished integration
-  // into settings, verify we see all results here, and that opening works
-  // correctly for the new URLs.
-  search_handler_->Search(query, kMaxResults,
+  search_handler_->Search(query, kNumRequestedResults,
                           chromeos::settings::mojom::ParentResultBehavior::
                               kDoNotIncludeParentResults,
                           base::BindOnce(&OsSettingsProvider::OnSearchReturned,
@@ -165,7 +162,7 @@ void OsSettingsProvider::Start(const base::string16& query) {
 
 void OsSettingsProvider::OnSearchReturned(
     std::vector<chromeos::settings::mojom::SearchResultPtr> results) {
-  DCHECK_LE(results.size(), kMaxResults);
+  DCHECK_LE(results.size(), kNumRequestedResults);
 
   std::vector<SearchResultPtr> clean_results = DeduplicateResults(results);
   std::sort(clean_results.begin(), clean_results.end(),
@@ -177,7 +174,8 @@ void OsSettingsProvider::OnSearchReturned(
   // Instead, we are gluing at most two to the top of the search box. Consider
   // ranking these with other results in the next version of the feature.
   SearchProvider::Results search_results;
-  for (size_t i = 0; i < clean_results.size(); ++i) {
+  const size_t num_results = std::min(clean_results.size(), kMaxShownResults);
+  for (size_t i = 0; i < num_results; ++i) {
     const auto& result = clean_results[i];
     const float score = 1.0f - i * kScoreEps;
     search_results.emplace_back(