[Hashed logging] Log the last-opened app.

This CL adds the most recently launched app to the info included in a
hashed logging event.

Note: there are now a couple of string manipulation functions in
search_controller.cc that probably don't belong there, and are
also duplicated elsewhere. I'll refactor them out into the utilities
class in a separate CL.

Bug: 951287
Change-Id: I0ea7379339aa1ae25788a6c0cc6af73f38a0f004
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1634029Reviewed-by: Jia Meng <jiameng@chromium.org>
Reviewed-by: calamity <calamity@chromium.org>
Commit-Queue: Tony Yeoman <tby@chromium.org>
Cr-Commit-Position: refs/heads/master@{#664134}

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

@@ -38,6 +38,8 @@ namespace {
 constexpr char kLogDisplayTypeClickedResultZeroState[] =
     "Apps.LogDisplayTypeClickedResultZeroState";
 
+// TODO(931149): Move the string manipulation utilities into a helper class.
+
 // Normalizes training targets by removing any scheme prefix and trailing slash:
 // "arc://[id]/" to "[id]". This is necessary because apps launched from
 // different parts of the launcher have differently formatted IDs.
@@ -52,6 +54,16 @@ std::string NormalizeId(const std::string& id) {
   return result;
 }
 
+// Remove the Arc app shortcut label from an app ID, if it exists, so that
+// "[app]/[label]" becomes "[app]".
+std::string RemoveAppShortcutLabel(const std::string& id) {
+  std::string result(id);
+  std::size_t delimiter_index = result.find_last_of('/');
+  if (delimiter_index != std::string::npos)
+    result.erase(delimiter_index);
+  return result;
+}
+
 }  // namespace
 
 SearchController::SearchController(AppListModelUpdater* model_updater,
@@ -189,10 +201,18 @@ void SearchController::Train(const std::string& id, RankingItemType type) {
       launch_type = ChromeOSAppListLaunchEventProto::RESULTS_LIST;
     }
 
-    // TODO(951287): Record the last-used domain and app.
+    // TODO(951287): Record the last-used domain.
     AppListLaunchRecorder::GetInstance()->Record(
         {launch_type, NormalizeId(id), base::UTF16ToUTF8(last_query_),
-         std::string(), std::string()});
+         std::string(), last_launched_app_id_});
+
+    // Only record the last launched app if the hashed logging feature flag is
+    // enabled, because it is only used by hashed logging.
+    if (type == RankingItemType::kApp) {
+      last_launched_app_id_ = NormalizeId(id);
+    } else if (type == RankingItemType::kArcAppShortcut) {
+      last_launched_app_id_ = RemoveAppShortcutLabel(NormalizeId(id));
+    }
   }
 
   for (const auto& provider : providers_)

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

@@ -80,6 +80,10 @@ class SearchController {
   // The query associated with the most recent search.
   base::string16 last_query_;
 
+  // The ID of the most recently launched app. This is used for app list launch
+  // recording.
+  std::string last_launched_app_id_;
+
   std::unique_ptr<Mixer> mixer_;
   using Providers = std::vector<std::unique_ptr<SearchProvider>>;
   Providers providers_;