Ticket #28612: 28612.1.patch

src/wp-includes/js/tinymce/plugins/wordpress/plugin.js

@@ -566 +566 @@
                                 wp.autosave.server.triggerSave();
                         }
                 } );
+
+                if ( window.getUserSetting( 'editor_plain_text_paste_warning' ) > 1 ) {
+                        editor.settings.paste_plaintext_inform = false;
+                }
         } );
 
+        editor.on( 'PastePlainTextToggle', function( event ) {
+                // Warn twice, then stop.
+                if ( event.state === true ) {
+                        var times = parseInt( window.getUserSetting( 'editor_plain_text_paste_warning' ), 10 ) || 0;
+
+                        if ( times < 2 ) {
+                                window.setUserSetting( 'editor_plain_text_paste_warning', ++times );
+                        }
+                }
+        });
+
         /**
          * Experimental: create a floating toolbar.
          * This functionality will change in the next releases. Not recommended for use by plugins.