Implement the chrome.passwordsPrivate API.

chrome/common/extensions/api/passwords_private.idl

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Use the <code>chrome.passwordsPrivate</code> API to add or remove password
 // data from the settings UI.
 namespace passwordsPrivate {
   // Pair of origin URL and login saved for that URL.
   dictionary LoginPair {
     // The human-readable origin for the URL where the password is used.
     DOMString originUrl;
 
     // The username used in conjunction with the saved password.
     DOMString username;
   };
 
   // Entry used to display a password in the settings UI.
   dictionary PasswordUiEntry {
     // The login information for this entry.
     LoginPair loginPair;
 
     // The number of characters in the password; used to display placeholder
     // dots in the UI.
     long numCharactersInPassword;
 
     // Text shown if the password was obtained via a federated identity.
     DOMString? federationText;
   };
 
+  // Dictionary passed to listeners for the onPlaintextPasswordRetrieved event.
+  dictionary PlaintextPasswordEventParameters {
+    // The LoginPair associated with the retrieved password.
+    LoginPair loginPair;
+
+    // The password in plaintext.
+    DOMString plaintextPassword;
+  };
+
   callback CanAccountBeManagedCallback = void(boolean canAccountBeManaged);
-  callback PlaintextPasswordCallback = void(DOMString plaintextPassword);
 
   interface Functions {
     // Determines whether account's passwords can be managed via
     // https://passwords.google.com/settings/passwords.
     //
     // |callback|: Callback which will be passed the boolean of whether the
     //     account can be managed.
     static void canPasswordAccountBeManaged(
         CanAccountBeManagedCallback callback);
 
     // Removes the saved password corresponding to |loginPair|. If no saved
     // password for this pair exists, this function is a no-op.
     //
     // |loginPair|: The LoginPair corresponding to the entry to remove.
     static void removeSavedPassword(LoginPair loginPair);
 
     // Removes the saved password exception corresponding to |exceptionUrl|. If
     // no exception with this URL exists, this function is a no-op.
     //
     // |exceptionUrl|: The URL corresponding to the exception to remove.
     static void removePasswordException(DOMString exceptionUrl);
 
     // Returns the plaintext password corresponding to |loginPair|. Note that on
     // some operating systems, this call may result in an OS-level
-    // reauthentication.
+    // reauthentication. Once the password has been fetched, it will be returned
+    // via the onPlaintextPasswordRetrieved event.
     //
     // |loginPair|: The LoginPair corresponding to the entry whose password
     //     is to be returned.
-    // |callback|: Callback which will be passed the plaintext password.
-    static void getPlaintextPassword(
-        LoginPair loginPair, PlaintextPasswordCallback callback);
+    static void requestPlaintextPassword(LoginPair loginPair);
   };
 
   interface Events {
     // Fired when the saved passwords list has changed, meaning that an entry
     // has been added or removed. Note that this event fires as soon as a
     //  listener is added.
     //
     // |entries|: The updated list of password entries.
     static void onSavedPasswordsListChanged(PasswordUiEntry[] entries);
 
     // Fired when the password exceptions list has changed, meaning that an
     // entry has been added or removed. Note that this event fires as soon as a
-    //  listener is added.
+    // listener is added.
     //
     // |exceptions|: The updated list of password exceptions.
     static void onPasswordExceptionsListChanged(DOMString[] exceptions);
+
+    // Fired when a plaintext password has been fetched in response to a call to
+    // chrome.passwordsPrivate.requestPlaintextPassword().
+    //
+    // |loginPair|: The LoginPair whose password was found.
+    // |plaintextPassword|: The plaintext password which was retrieved.
+    static void onPlaintextPasswordRetrieved(
+        PlaintextPasswordEventParameters dict);
   };
 };