Index: src/wp-admin/edit-form-advanced.php
===================================================================
--- src/wp-admin/edit-form-advanced.php	(revision 28158)
+++ src/wp-admin/edit-form-advanced.php	(working copy)
@@ -485,7 +485,7 @@
 ?>
 <div id="postdivrich" class="postarea edit-form-section">
 
-<?php wp_editor( $post->post_content, 'content', array(
+<?php $wp_editor_args = array(
 	'dfw' => true,
 	'drag_drop_upload' => true,
 	'tabfocus_elements' => 'insert-media-button,save-post',
@@ -493,8 +493,19 @@
 	'tinymce' => array(
 		'resize' => false,
 		'add_unload_trigger' => false,
-	),
-) ); ?>
+		),
+	);
+/**
+* Filter the default args that setup the TinyMCE Editor on the Edit Posts page.
+*
+* @since 3.9.1
+*
+* @param array  $wp_editor_args Array of configuration arguments for TinyMCE.
+*/
+
+$wp_editor_args = apply_filters( 'edit_form_editor_args', $wp_editor_args );
+
+wp_editor( $post->post_content, 'content', $wp_editor_args ); ?>
 <table id="post-status-info"><tbody><tr>
 	<td id="wp-word-count"><?php printf( __( 'Word count: %s' ), '<span class="word-count">0</span>' ); ?></td>
 	<td class="autosave-info">