[Autofill] Pass struct by const-reference.

components/autofill/browser/form_structure.h

Index: components/autofill/browser/form_structure.h
diff --git a/components/autofill/browser/form_structure.h b/components/autofill/browser/form_structure.h
index 9372ce5ee0446cf923695e555f71cefac6031e6f..e6545600d7bf228f7d53120218b8cd54916719e6 100644
--- a/components/autofill/browser/form_structure.h
+++ b/components/autofill/browser/form_structure.h
@@ -202,7 +202,7 @@ class FormStructure {
   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;