Add "previewing on hover" support for password field.

components/password_manager/core/browser/password_manager_driver.h

Index: components/password_manager/core/browser/password_manager_driver.h
diff --git a/components/password_manager/core/browser/password_manager_driver.h b/components/password_manager/core/browser/password_manager_driver.h
index 8087af7a9367aa78460eb6c80ad753bb35c98984..78e38097b1c847092110fb6a9ff7f4b4c746d9f4 100644
--- a/components/password_manager/core/browser/password_manager_driver.h
+++ b/components/password_manager/core/browser/password_manager_driver.h
@@ -51,6 +51,15 @@ class PasswordManagerDriver {
       const base::string16& username,
       const base::string16& password) = 0;
 
+  // Tells the driver to select the password autofill suggestion for |username|
+  // and preview the password with |password|.

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

nit: "Tells the driver to preview filling form with the |username| and
|password|."

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

Done.

+  virtual void PreviewPasswordAutofillSuggestion(
+      const base::string16& username,
+      const base::string16& password) = 0;

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

nit: I'd recommend renaming these two methods to FillSuggestion() and
PreviewSuggestion().

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

Done.

+
+  // Clear previewed password and username fields.
+  virtual void ClearPasswordPreviewedForm() = 0;

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

nit: "ClearPreviewedForm"

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

Done.

+
   // Returns the PasswordGenerationManager associated with this instance.
   virtual PasswordGenerationManager* GetPasswordGenerationManager() = 0;