Fix possible crash in FinalizeInstantQuery() if AddMatchToMap() fails.

chrome/browser/autocomplete/search_provider.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 "chrome/browser/autocomplete/search_provider.h"
 
 #include <algorithm>
 #include <cmath>
 
 #include "base/callback.h"
@@ skipping 118 matching lines @@
     return;
   }
 
   default_provider_suggest_text_ = suggest_text;
 
   string16 adjusted_input_text(input_text);
   AutocompleteInput::RemoveForcedQueryStringIfNecessary(input_.type(),
                                                         &adjusted_input_text);
 
   const string16 text = adjusted_input_text + suggest_text;
+  bool results_updated = false;
   // Remove any matches that are identical to |text|. We don't use the
   // destination_url for comparison as it varies depending upon the index passed
   // to TemplateURL::ReplaceSearchTerms.
   for (ACMatches::iterator i = matches_.begin(); i != matches_.end();) {
     if (((i->type == AutocompleteMatch::SEARCH_HISTORY) ||
          (i->type == AutocompleteMatch::SEARCH_SUGGEST)) &&
         (i->fill_into_edit == text)) {
       i = matches_.erase(i);
+      results_updated = true;
     } else {
       ++i;
     }
   }
 
   // Add the new instant suggest result. We give it a rank higher than
   // SEARCH_WHAT_YOU_TYPED so that it gets autocompleted.
   int did_not_accept_default_suggestion = default_suggest_results_.empty() ?
         TemplateURLRef::NO_SUGGESTIONS_AVAILABLE :
         TemplateURLRef::NO_SUGGESTION_CHOSEN;
   MatchMap match_map;
   AddMatchToMap(text, adjusted_input_text,
                 CalculateRelevanceForWhatYouTyped() + 1,
                 AutocompleteMatch::SEARCH_SUGGEST,
                 did_not_accept_default_suggestion, false, &match_map);
-  DCHECK_EQ(1u, match_map.size());
-  matches_.push_back(match_map.begin()->second);
+  if (!match_map.empty()) {
+    matches_.push_back(match_map.begin()->second);
+    results_updated = true;
+  }
 
-  listener_->OnProviderUpdate(true);
+  if (results_updated || done_)
+    listener_->OnProviderUpdate(results_updated);
 }
 
 void SearchProvider::Start(const AutocompleteInput& input,
                            bool minimal_changes) {
   matches_.clear();
 
   instant_finalized_ =
       (input.matches_requested() != AutocompleteInput::ALL_MATCHES);
 
   // Can't return search/suggest results for bogus input or without a profile.
@@ skipping 814 matching lines @@
 
   return match;
 }
 
 void SearchProvider::UpdateDone() {
   // We're done when there are no more suggest queries pending (this is set to 1
   // when the timer is started) and we're not waiting on instant.
   done_ = ((suggest_results_pending_ == 0) &&
            (instant_finalized_ || !InstantController::IsEnabled(profile_)));
 }