Assume all providers may give zero suggest responses.

chrome/browser/autocomplete/builtin_provider.h

Index: chrome/browser/autocomplete/builtin_provider.h
diff --git a/chrome/browser/autocomplete/builtin_provider.h b/chrome/browser/autocomplete/builtin_provider.h
index d81cee91eb69fa9dedb55c70697ada380700033b..a53068da9820244ffe70c2c01aa770d080a2d21b 100644
--- a/chrome/browser/autocomplete/builtin_provider.h
+++ b/chrome/browser/autocomplete/builtin_provider.h
@@ -20,7 +20,9 @@ class BuiltinProvider : public AutocompleteProvider {
   BuiltinProvider();
 
   // AutocompleteProvider:
-  void Start(const AutocompleteInput& input, bool minimal_changes) override;
+  void Start(const AutocompleteInput& input,
+             bool minimal_changes,
+             bool on_focus) override;
 
  private:
   ~BuiltinProvider() override;