Initial open-source release

PiperOrigin-RevId: 271685289
diff --git a/preamble.js.lds b/preamble.js.lds
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+/*
+ * Copyright 2019 Google LLC
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+/* mock crypto module for benchmarks and unit tests or std::random_device fails at runtime */
+var crypto = { getRandomValues: function(array) { for (var i = 0; i < array.length; i++) array[i] = (Math.random()*256)|0 } };