Add histograms for notices about other forms of browsing history

ios/chrome/browser/ui/webui/history/browsing_history_handler.cc

 // Copyright 2016 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 "ios/chrome/browser/ui/webui/history/browsing_history_handler.h"
 
 #include <stddef.h>
 
 #include <set>
 
@@ skipping 114 matching lines @@
       default:
         *type = kDeviceTypeLaptop;
     }
     return;
   }
 
   *name = l10n_util::GetStringUTF8(IDS_HISTORY_UNKNOWN_DEVICE);
   *type = kDeviceTypeLaptop;
 }
 
+void RecordMetricsForNoticeAboutOtherFormsOfBrowsingHistory(bool shown) {
+  UMA_HISTOGRAM_BOOLEAN("History.ShownHeaderAboutOtherFormsOfBrowsingHistory",
+                        shown);
+}
+
 }  // namespace
 
 BrowsingHistoryHandler::HistoryEntry::HistoryEntry(
     BrowsingHistoryHandler::HistoryEntry::EntryType entry_type,
     const GURL& url,
     const base::string16& title,
     base::Time time,
     const std::string& client_id,
     bool is_search_result,
     const base::string16& snippet,
@@ skipping 225 matching lines @@
             browser_state);
     // Test the existence of other forms of browsing history.
     browsing_data_ui::ShouldShowNoticeAboutOtherFormsOfBrowsingHistory(
         sync_service, web_history,
         base::Bind(
             &BrowsingHistoryHandler::OtherFormsOfBrowsingHistoryQueryComplete,
             weak_factory_.GetWeakPtr()));
 
     // Set this to false until the results actually arrive.
     results_info_value_.SetBoolean("hasSyncedResults", false);
+  } else {
+    // The notice could not have been shown, because there is no web history.
+    RecordMetricsForNoticeAboutOtherFormsOfBrowsingHistory(false);
   }
 }
 
 void BrowsingHistoryHandler::HandleQueryHistory(const base::ListValue* args) {
   history::QueryOptions options;
 
   // Parse the arguments from JavaScript. There are five required arguments:
   // - the text to search for (may be empty)
   // - the offset from which the search should start (in multiples of week or
   //   month, set by the next argument).
@@ skipping 351 matching lines @@
   }
   has_synced_results_ = results_value != nullptr;
   results_info_value_.SetBoolean("hasSyncedResults", has_synced_results_);
   if (!query_task_tracker_.HasTrackedTasks())
     ReturnResultsToFrontEnd();
 }
 
 void BrowsingHistoryHandler::OtherFormsOfBrowsingHistoryQueryComplete(
     bool found_other_forms_of_browsing_history) {
   has_other_forms_of_browsing_history_ = found_other_forms_of_browsing_history;
+  RecordMetricsForNoticeAboutOtherFormsOfBrowsingHistory(
+      has_other_forms_of_browsing_history_);
   web_ui()->CallJavascriptFunction(
       "showNotification", base::FundamentalValue(has_synced_results_),
       base::FundamentalValue(has_other_forms_of_browsing_history_));
 }
 
 void BrowsingHistoryHandler::RemoveComplete() {
   urls_to_be_deleted_.clear();
 
   // Notify the page that the deletion request is complete, but only if a web
   // history delete request is not still pending.
@@ skipping 68 matching lines @@
 
 void BrowsingHistoryHandler::OnURLsDeleted(
     history::HistoryService* history_service,
     bool all_history,
     bool expired,
     const history::URLRows& deleted_rows,
     const std::set<GURL>& favicon_urls) {
   if (all_history || DeletionsDiffer(deleted_rows, urls_to_be_deleted_))
     web_ui()->CallJavascriptFunction("historyDeleted");
 }