[Password manager] Recognise squashed login+sign-up forms

components/autofill/core/common/password_form.h

Index: components/autofill/core/common/password_form.h
diff --git a/components/autofill/core/common/password_form.h b/components/autofill/core/common/password_form.h
index 783eda54786c8e433d20807d7799e65c5523b62b..e927485e71393d8f4f8dcf10a4dc3b117367de2d 100644
--- a/components/autofill/core/common/password_form.h
+++ b/components/autofill/core/common/password_form.h
@@ -59,6 +59,24 @@ struct PasswordForm {
     SCHEME_LAST = SCHEME_OTHER
   } scheme;
 
+  // A layout characterises the sequence of non-password text and password input
+  // fields of which the form is made. It is defined as a regular language over
+  // the alphabet {N, P} (indicating Non-password and Password fields); e.g., a
+  // layout NPN+PP characterises all forms which have a single non-password
+  // field followed by a single password field, followed by 1 or more
+  // non-password fields, followed by 2 password fields.
+  // For most forms we do not care about the layout (those have LAYOUT_OTHER),
+  // but for special cases we might need to know it: e.g., the NPN+PP forms can
+  // be a login form glued to a sign-up form, and the "N+" part is what
+  // distinguishes such forms from change-password forms.
+  // A layout is useful for understanding parsed forms and deciding whether to
+  // fill them, but it is not stored.
+  enum class Layout {
+    LAYOUT_OTHER,
+    LAYOUT_LOGIN_AND_SIGNUP,  // NPN+PP
+    LAYOUT_LAST = LAYOUT_LOGIN_AND_SIGNUP
+  };
+
   // The "Realm" for the sign-on. This is scheme, host, port for SCHEME_HTML.
   // Dialog based forms also contain the HTTP realm. Android based forms will
   // contain a string of the form "android://<hash of cert>@<package name>"
@@ -238,6 +256,9 @@ struct PasswordForm {
   // Once user selects this credential the flag is reseted.
   bool skip_zero_click;
 
+  // The layout as determined during parsing. Default value is LAYOUT_OTHER.
+  Layout layout;
+
   // Returns true if this match was found using public suffix matching.
   bool IsPublicSuffixMatch() const;
 
@@ -255,6 +276,7 @@ typedef std::map<base::string16, PasswordForm*> PasswordFormMap;
 typedef std::map<base::string16, const PasswordForm*> ConstPasswordFormMap;
 
 // For testing.
+std::ostream& operator<<(std::ostream& os, PasswordForm::Layout layout);
 std::ostream& operator<<(std::ostream& os,
                          const autofill::PasswordForm& form);