Conditionally change the editor stylesheet loaded in TinyMCE

gistfile1.php

<?php
/**
 * Conditionally change the editor stylesheet loaded in TinyMCE
 * 
 * Few things to note. All this is done inside after_theme_setup (or equivilant).
 * Before this is executed we still use are normal add_editor_style( 'css/editor-style.css' );
 * to set the default stylesheet. Lastly the example below only loads on edit post
 * because loading on new posts wouldn't help since the template hasn't been set. It can
 * be loaded on new posts though, reference the codex link below.
 *
 * @link http://codex.wordpress.org/Function_Reference/add_editor_style
 */
function ja_editor_style_conditional() {

	global $post;

	// Edit post (pre_get_posts).
	if ( stristr( $_SERVER['REQUEST_URI'], 'post.php' ) !== false && is_object( $post ) && 'page' == get_post_type( $post->ID ) ) {

		if ( get_page_template_slug( $post->ID ) == 'template-product.php' ) {
			add_editor_style( 'css/editor-style-product.css' );
		}
	}
}
add_action( 'pre_get_posts', 'ja_editor_style_conditional' );