Index: src/wp-includes/class-wp-editor.php
===================================================================
--- src/wp-includes/class-wp-editor.php	(revision 27494)
+++ src/wp-includes/class-wp-editor.php	(working copy)
@@ -1091,6 +1091,9 @@
 			<div id="wp-link-update">
 				<input type="submit" value="<?php esc_attr_e( 'Add Link' ); ?>" class="button-primary" id="wp-link-submit" name="wp-link-submit">
 			</div>
+			<div id="wp-link-cancel">
+				<a class="submitdelete deletion" href="#"><?php _e( 'Cancel' ); ?></a>
+			</div>
 		</div>
 		</form>
 		</div>
Index: src/wp-includes/js/wplink.js
===================================================================
--- src/wp-includes/js/wplink.js	(revision 27494)
+++ src/wp-includes/js/wplink.js	(working copy)
@@ -38,7 +38,7 @@
 				event.preventDefault();
 				wpLink.update();
 			});
-			inputs.close.add( inputs.backdrop ).click( function( event ) {
+			inputs.close.add( inputs.backdrop ).add( '#wp-link-cancel a' ).click( function( event ) {
 				event.preventDefault();
 				wpLink.close();
 			});