Updated the files.

my-app/node_modules/webpack-sources/lib/SizeOnlySource.js

@@ -0,0 +1,42 @@
+/*
+	MIT License http://www.opensource.org/licenses/mit-license.php
+	Author Tobias Koppers @sokra
+*/
+"use strict";
+
+const Source = require("./Source");
+
+class SizeOnlySource extends Source {
+	constructor(size) {
+		super();
+		this._size = size;
+	}
+
+	_error() {
+		return new Error(
+			"Content and Map of this Source is not available (only size() is supported)"
+		);
+	}
+
+	size() {
+		return this._size;
+	}
+
+	source() {
+		throw this._error();
+	}
+
+	buffer() {
+		throw this._error();
+	}
+
+	map(options) {
+		throw this._error();
+	}
+
+	updateHash() {
+		throw this._error();
+	}
+}
+
+module.exports = SizeOnlySource;