Index: src/wp-includes/l10n.php
===================================================================
--- src/wp-includes/l10n.php	(revision 43972)
+++ src/wp-includes/l10n.php	(working copy)
@@ -900,8 +900,12 @@
 
 	$obj = $wp_scripts->registered[ $handle ];
 
+	$src = $obj->src;
+	if ( ! preg_match( '|^(https?:)?//|', $src ) && ! ( $wp_scripts->content_url && 0 === strpos( $src, $wp_scripts->content_url ) ) ) {
+		$src = $wp_scripts->base_url . $src;
+	}
 	/** This filter is documented in wp-includes/class.wp-scripts.php */
-	$src = esc_url( apply_filters( 'script_loader_src', $obj->src, $handle ) );
+	$src = esc_url( apply_filters( 'script_loader_src', $src, $handle ) );
 
 	$relative       = false;
 	$languages_path = WP_LANG_DIR;
@@ -916,7 +920,7 @@
 		( ! isset( $src_url['host'] ) || $src_url['host'] !== $content_url['host'] )
 	) {
 		// Make the src relative the specific plugin or theme.
-		$relative = trim( substr( $src, strlen( $content_url['path'] ) ), '/' );
+		$relative = trim( substr( $src_url['path'], strlen( $content_url['path'] ) ), '/' );
 		$relative = explode( '/', $relative );
 
 		$languages_path = WP_LANG_DIR . '/' . $relative[0];
@@ -928,7 +932,7 @@
 			$relative = trim( $src_url['path'], '/' );
 		} elseif ( ( strpos( $src_url['path'], $site_url['path'] ) === 0 ) ) {
 			// Make the src relative to the WP root.
-			$relative = substr( $src, strlen( $site_url['path'] ) );
+			$relative = substr( $src_url['path'], strlen( $site_url['path'] ) );
 			$relative = trim( $relative, '/' );
 		}
 	}