Adding performance tests for HQP that represent importance of optimising HistoryItemsForTerms method

components/omnibox/browser/autocomplete_controller.cc

 // Copyright (c) 2012 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 "components/omnibox/browser/autocomplete_controller.h"
 
 #include <stddef.h>
 #include <set>
 #include <string>
 #include <utility>
@@ skipping 223 matching lines @@
   // to ensure they won't call us back if they outlive us.  (Practically,
   // calling Stop() should also cancel those tasks and make it so that we hold
   // the only refs.)  We also don't want to bother notifying anyone of our
   // result changes here, because the notification observer is in the midst of
   // shutdown too, so we don't ask Stop() to clear |result_| (and notify).
   result_.Reset();  // Not really necessary.
   Stop(false);
 }
 
 void AutocompleteController::Start(const AutocompleteInput& input) {
+  SCOPED_UMA_HISTOGRAM_TIMER("Omnibox.StartSearchToFirstResultsTime");
   TRACE_EVENT1("omnibox", "AutocompleteController::Start",
                "text", base::UTF16ToUTF8(input.text()));
   const base::string16 old_input_text(input_.text());
   const bool old_allow_exact_keyword_match = input_.allow_exact_keyword_match();
   const bool old_want_asynchronous_matches = input_.want_asynchronous_matches();
   const bool old_from_omnibox_focus = input_.from_omnibox_focus();
   input_ = input;
 
   // See if we can avoid rerunning autocomplete when the query hasn't changed
   // much.  When the user presses or releases the ctrl key, the desired_tld
@@ skipping 412 matching lines @@
   expire_timer_.Stop();
   stop_timer_.Stop();
   done_ = true;
   if (clear_result && !result_.empty()) {
     result_.Reset();
     // NOTE: We pass in false since we're trying to only clear the popup, not
     // touch the edit... this is all a mess and should be cleaned up :(
     NotifyChanged(false);
   }
 }