Add "previewing on hover" support for password field.

components/autofill/content/renderer/form_autofill_util.h

Index: components/autofill/content/renderer/form_autofill_util.h
diff --git a/components/autofill/content/renderer/form_autofill_util.h b/components/autofill/content/renderer/form_autofill_util.h
index 0f0f6c2e134ba13cfde638658a9925f5056605d8..4a6abf55e4738eb201d0d689b346b084ce068cff 100644
--- a/components/autofill/content/renderer/form_autofill_util.h
+++ b/components/autofill/content/renderer/form_autofill_util.h
@@ -146,10 +146,11 @@ void PreviewForm(const FormData& form,
 
 // Clears the placeholder values and the auto-filled background for any fields
 // in the form containing |node| that have been previewed.  Resets the
-// autofilled state of |node| to |was_autofilled|.  Returns false if the form is
-// not found.
+// autofilled state of |node| to |was_autofilled| and password node autofilled
+// state to |was_password_autofilled|.  Returns false if the form is not found.
 bool ClearPreviewedFormWithElement(const blink::WebFormControlElement& element,
-                                   bool was_autofilled);
+                                   bool was_autofilled,
+                                   bool was_password_autofilled);

[Ilya Sherman, 2014/05/13 00:44:05]

There might be multiple passwords.  I think it might be easiest not to call this
method at all for password forms, since we know there are only two elements to
deal with in that case.  So, within the PasswordAutofillAgent class's private
implementation, you could have a simple ClearPreview() function.  That function
would pick out the username and password elements, and:
  (1) Clear their suggested values.
  (2) Restore their previous autofilled or not-autofilled states.
  (3) Position the cursor at the end of the username field.

(3) is admittedly a bit of nontrivial repeated code; but on the whole, I think
the result is cleaner with all of the logic internalized within the
PasswordAutofillAgent class.

[ziran.sun, 2014/05/14 15:35:12]

Done.

 
 // Returns true if |form| has any auto-filled fields.
 bool FormWithElementIsAutofilled(const blink::WebInputElement& element);