Assume all providers may give zero suggest responses.

components/omnibox/search_provider.cc

 // Copyright 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/search_provider.h"
 
 #include <algorithm>
 #include <cmath>
 
 #include "base/base64.h"
@@ skipping 171 matching lines @@
 
 // static
 ACMatches::iterator SearchProvider::FindTopMatch(ACMatches* matches) {
   ACMatches::iterator it = matches->begin();
   while ((it != matches->end()) && !it->allowed_to_be_default_match)
     ++it;
   return it;
 }
 
 void SearchProvider::Start(const AutocompleteInput& input,
-                           bool minimal_changes) {
+                           bool minimal_changes,
+                           bool on_focus) {
   // Do our best to load the model as early as possible.  This will reduce
   // odds of having the model not ready when really needed (a non-empty input).
   TemplateURLService* model = providers_.template_url_service();
   DCHECK(model);
   model->Load();
 
   matches_.clear();
   field_trial_triggered_ = false;
 
   // Can't return search/suggest results for bogus input.
-  if (input.type() == metrics::OmniboxInputType::INVALID) {
+  if (on_focus || input.type() == metrics::OmniboxInputType::INVALID) {
     Stop(true);
     return;
   }
 
   keyword_input_ = input;
   const TemplateURL* keyword_provider =
       KeywordProvider::GetSubstitutingTemplateURLForInput(model,
                                                           &keyword_input_);
   if (keyword_provider == NULL)
     keyword_input_.Clear();
@@ skipping 1235 matching lines @@
   for (MatchMap::const_iterator i(map.begin()); i != map.end(); ++i)
     matches.push_back(i->second);
   std::sort(matches.begin(), matches.end(), &AutocompleteMatch::MoreRelevant);
 
   // If there is a top scoring entry, find the corresponding answer.
   if (!matches.empty())
     return answers_cache_.GetTopAnswerEntry(matches[0].contents);
 
   return AnswersQueryData();
 }