Add metadata to content::PasswordForm to keep track of the password usage.

content/public/common/password_form.h

Index: content/public/common/password_form.h
diff --git a/content/public/common/password_form.h b/content/public/common/password_form.h
index 21b2e56769858a01a7bd54724628b14a06fbb786..0f0ea4ce1d0543acdffe36354ab7289ffa58f4ad 100644
--- a/content/public/common/password_form.h
+++ b/content/public/common/password_form.h
@@ -157,6 +157,12 @@ struct CONTENT_EXPORT PasswordForm {
   // The form type. Not used yet. Please see http://crbug.com/152422
   Type type;
 
+  // The number of times that this username/password has been used to
+  // authenticate the user.
+  //
+  // When parsing an HTML form, this is not used.
+  int times_used;
+
   PasswordForm();
   ~PasswordForm();
 };