Index: src/wp-admin/includes/upgrade.php
===================================================================
--- src/wp-admin/includes/upgrade.php	(revision 26508)
+++ src/wp-admin/includes/upgrade.php	(working copy)
@@ -412,6 +412,8 @@
 
 	maybe_disable_automattic_widgets();
 
+	maybe_disable_mp6_thx38_dash();
+
 	update_option( 'db_version', $wp_db_version );
 	update_option( 'db_upgraded', true );
 }
@@ -1990,6 +1992,23 @@
 }
 
 /**
+ * Disables MP6, THX38, and DASH plugins, which were merged into core.
+ *
+ * @since 3.8.0
+ */
+function maybe_disable_mp6_thx38_dash() {
+	$plugins = __get_option( 'active_plugins' );
+
+	foreach ( (array) $plugins as $plugin ) {
+		if ( in_array( basename( $plugin ), array( 'mp6.php', 'thx-38.php', 'dashboard.php' ) ) ) {
+			array_splice( $plugins, array_search( $plugin, $plugins ), 1 );
+			update_option( 'active_plugins', $plugins );
+			break;
+		}
+	}
+}
+
+/**
  * Disables the Link Manager on upgrade, if at the time of upgrade, no links exist in the DB.
  *
  * @since 3.5.0