[Autofill] Pass struct by const-reference.

components/autofill/browser/form_structure.h

 // Copyright (c) 2011 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 COMPONENTS_AUTOFILL_BROWSER_FORM_STRUCTURE_H_
 #define COMPONENTS_AUTOFILL_BROWSER_FORM_STRUCTURE_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 184 matching lines @@
   // include multiple fields of the same autofill type (with some exceptions, as
   // described in the implementation).  Sections are furthermore distinguished
   // as either credit card or non-credit card sections.
   // If |has_author_specified_sections| is true, only the second pass --
   // distinguishing credit card sections from non-credit card ones -- is made.
   void IdentifySections(bool has_author_specified_sections);
 
   bool IsAutocheckoutEnabled() const;
 
   // Returns true if field should be skipped when talking to Autofill server.
-  bool ShouldSkipField(const FormFieldData field) const;
+  bool ShouldSkipField(const FormFieldData& field) const;
 
   // Returns the minimal number of fillable fields required to start autofill.
   size_t RequiredFillableFields() const;
   size_t active_field_count() const;
 
   // The name of the form.
   base::string16 form_name_;
 
   // The source URL.
   GURL source_url_;
@@ skipping 37 matching lines @@
 
   // Whether or not this form was filled by Autocheckout.
   bool filled_by_autocheckout_;
 
   DISALLOW_COPY_AND_ASSIGN(FormStructure);
 };
 
 }  // namespace autofill
 
 #endif  // COMPONENTS_AUTOFILL_BROWSER_FORM_STRUCTURE_H_