Assume all providers may give zero suggest responses.

chrome/browser/autocomplete/shortcuts_provider.h

 // 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.
 
 #ifndef CHROME_BROWSER_AUTOCOMPLETE_SHORTCUTS_PROVIDER_H_
 #define CHROME_BROWSER_AUTOCOMPLETE_SHORTCUTS_PROVIDER_H_
 
 #include <map>
 #include <set>
 #include <string>
@@ skipping 10 matching lines @@
 // suggestion for a given search term the higher will be that suggestion's
 // ranking for future uses of that search term.
 class ShortcutsProvider
     : public AutocompleteProvider,
       public ShortcutsBackend::ShortcutsBackendObserver {
  public:
   explicit ShortcutsProvider(Profile* profile);
 
   // Performs the autocompletion synchronously. Since no asynch completion is
   // performed |minimal_changes| is ignored.
-  void Start(const AutocompleteInput& input, bool minimal_changes) override;
+  void Start(const AutocompleteInput& input,
+             bool minimal_changes,
+             bool called_due_to_focus) override;
 
   void DeleteMatch(const AutocompleteMatch& match) override;
 
  private:
   friend class ClassifyTest;
   friend class ShortcutsProviderTest;
   FRIEND_TEST_ALL_PREFIXES(ShortcutsProviderTest, CalculateScore);
 
   typedef std::multimap<base::char16, base::string16> WordMap;
 
@@ skipping 60 matching lines @@
 
   // The default max relevance unless overridden by a field trial.
   static const int kShortcutsProviderDefaultMaxRelevance;
 
   Profile* profile_;
   std::string languages_;
   bool initialized_;
 };
 
 #endif  // CHROME_BROWSER_AUTOCOMPLETE_SHORTCUTS_PROVIDER_H_