Index: wp-includes/general-template.php
===================================================================
--- wp-includes/general-template.php	(revision 40333)
+++ wp-includes/general-template.php	(working copy)
@@ -391,6 +391,8 @@
  *     @type string $id_password    ID attribute value for the password field. Default 'user_pass'.
  *     @type string $id_remember    ID attribute value for the remember field. Default 'rememberme'.
  *     @type string $id_submit      ID attribute value for the submit button. Default 'wp-submit'.
+ *     @type string placeholder_username Placeholder attribute value for the username field. Default empty.
+ *     @type string placeholder_password Placeholder attribute value for the password field. Default empty.
  *     @type bool   $remember       Whether to display the "rememberme" checkbox in the form.
  *     @type string $value_username Default value for the username field. Default empty.
  *     @type bool   $value_remember Whether the "Remember Me" checkbox should be checked by default.
@@ -413,6 +415,8 @@
 		'id_password' => 'user_pass',
 		'id_remember' => 'rememberme',
 		'id_submit' => 'wp-submit',
+		'placeholder_username' => '',
+		'placeholder_password' => '',
 		'remember' => true,
 		'value_username' => '',
 		// Set 'value_remember' to true to default the "Remember me" checkbox to checked.
@@ -472,11 +476,11 @@
 			' . $login_form_top . '
 			<p class="login-username">
 				<label for="' . esc_attr( $args['id_username'] ) . '">' . esc_html( $args['label_username'] ) . '</label>
-				<input type="text" name="log" id="' . esc_attr( $args['id_username'] ) . '" class="input" value="' . esc_attr( $args['value_username'] ) . '" size="20" />
+				<input type="text" name="log" id="' . esc_attr( $args['id_username'] ) . '" class="input" placeholder="' . esc_attr( $args['placeholder_username'] ) . '" value="' . esc_attr( $args['value_username'] ) . '" size="20" />
 			</p>
 			<p class="login-password">
 				<label for="' . esc_attr( $args['id_password'] ) . '">' . esc_html( $args['label_password'] ) . '</label>
-				<input type="password" name="pwd" id="' . esc_attr( $args['id_password'] ) . '" class="input" value="" size="20" />
+				<input type="password" name="pwd" id="' . esc_attr( $args['id_password'] ) . '" class="input" placeholder="' . esc_attr( $args['placeholder_password'] ) . '" value="" size="20" />
 			</p>
 			' . $login_form_middle . '
 			' . ( $args['remember'] ? '<p class="login-remember"><label><input name="rememberme" type="checkbox" id="' . esc_attr( $args['id_remember'] ) . '" value="forever"' . ( $args['value_remember'] ? ' checked="checked"' : '' ) . ' /> ' . esc_html( $args['label_remember'] ) . '</label></p>' : '' ) . '