Down-integrate from internal code base.
diff --git a/js/binary/constants.js b/js/binary/constants.js
new file mode 100644
index 0000000..a976e0b
--- /dev/null
+++ b/js/binary/constants.js
@@ -0,0 +1,320 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc. All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+// * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+// * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+// * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+/**
+ * @fileoverview This file contains constants and typedefs used by
+ * jspb.BinaryReader and BinaryWriter.
+ *
+ * @author aappleby@google.com (Austin Appleby)
+ */
+
+goog.provide('jspb.AnyFieldType');
+goog.provide('jspb.BinaryConstants');
+goog.provide('jspb.BinaryMessage');
+goog.provide('jspb.BuilderFunction');
+goog.provide('jspb.ByteSource');
+goog.provide('jspb.ClonerFunction');
+goog.provide('jspb.ConstBinaryMessage');
+goog.provide('jspb.ReaderFunction');
+goog.provide('jspb.RecyclerFunction');
+goog.provide('jspb.WriterFunction');
+
+goog.forwardDeclare('jspb.Message');
+goog.forwardDeclare('jsproto.BinaryExtension');
+
+
+
+/**
+ * Base interface class for all const messages. Does __not__ define any
+ * methods, as doing so on a widely-used interface defeats dead-code
+ * elimination.
+ * @interface
+ */
+jspb.ConstBinaryMessage = function() {};
+
+
+
+/**
+ * Base interface class for all messages. Does __not__ define any methods, as
+ * doing so on a widely-used interface defeats dead-code elimination.
+ * @interface
+ * @extends {jspb.ConstBinaryMessage}
+ */
+jspb.BinaryMessage = function() {};
+
+
+/**
+ * The types convertible to Uint8Arrays. Strings are assumed to be
+ * base64-encoded.
+ * @typedef {ArrayBuffer|Uint8Array|Array<number>|string}
+ */
+jspb.ByteSource;
+
+
+/**
+ * A field in jspb can be a scalar, a block of bytes, another proto, or an
+ * array of any of the above.
+ * @typedef {boolean|number|string|Uint8Array|
+ jspb.BinaryMessage|jsproto.BinaryExtension|
+ Array<jspb.AnyFieldType>}
+ */
+jspb.AnyFieldType;
+
+
+/**
+ * A builder function creates an instance of a message object.
+ * @typedef {function():!jspb.BinaryMessage}
+ */
+jspb.BuilderFunction;
+
+
+/**
+ * A cloner function creates a deep copy of a message object.
+ * @typedef {function(jspb.ConstBinaryMessage):jspb.BinaryMessage}
+ */
+jspb.ClonerFunction;
+
+
+/**
+ * A recycler function destroys an instance of a message object.
+ * @typedef {function(!jspb.BinaryMessage):void}
+ */
+jspb.RecyclerFunction;
+
+
+/**
+ * A reader function initializes a message using data from a BinaryReader.
+ * @typedef {function(!jspb.BinaryMessage, !jspb.BinaryReader):void}
+ */
+jspb.ReaderFunction;
+
+
+/**
+ * A writer function serializes a message to a BinaryWriter.
+ * @typedef {!function(!jspb.Message, !jspb.BinaryWriter):void |
+ * !function(!jspb.ConstBinaryMessage, !jspb.BinaryWriter):void}
+ */
+jspb.WriterFunction;
+
+
+/**
+ * Field type codes, taken from proto2/public/wire_format_lite.h.
+ * @enum {number}
+ */
+jspb.BinaryConstants.FieldType = {
+ INVALID: -1,
+ DOUBLE: 1,
+ FLOAT: 2,
+ INT64: 3,
+ UINT64: 4,
+ INT32: 5,
+ FIXED64: 6,
+ FIXED32: 7,
+ BOOL: 8,
+ STRING: 9,
+ GROUP: 10,
+ MESSAGE: 11,
+ BYTES: 12,
+ UINT32: 13,
+ ENUM: 14,
+ SFIXED32: 15,
+ SFIXED64: 16,
+ SINT32: 17,
+ SINT64: 18,
+
+ // Extended types for Javascript
+
+ FHASH64: 30, // 64-bit hash string, fixed-length encoding.
+ VHASH64: 31 // 64-bit hash string, varint encoding.
+};
+
+
+/**
+ * Wire-format type codes, taken from proto2/public/wire_format_lite.h.
+ * @enum {number}
+ */
+jspb.BinaryConstants.WireType = {
+ INVALID: -1,
+ VARINT: 0,
+ FIXED64: 1,
+ DELIMITED: 2,
+ START_GROUP: 3,
+ END_GROUP: 4,
+ FIXED32: 5
+};
+
+
+/**
+ * Translates field type to wire type.
+ * @param {jspb.BinaryConstants.FieldType} fieldType
+ * @return {jspb.BinaryConstants.WireType}
+ */
+jspb.BinaryConstants.FieldTypeToWireType = function(fieldType) {
+ var fieldTypes = jspb.BinaryConstants.FieldType;
+ var wireTypes = jspb.BinaryConstants.WireType;
+ switch (fieldType) {
+ case fieldTypes.INT32:
+ case fieldTypes.INT64:
+ case fieldTypes.UINT32:
+ case fieldTypes.UINT64:
+ case fieldTypes.SINT32:
+ case fieldTypes.SINT64:
+ case fieldTypes.BOOL:
+ case fieldTypes.ENUM:
+ case fieldTypes.VHASH64:
+ return wireTypes.VARINT;
+
+ case fieldTypes.DOUBLE:
+ case fieldTypes.FIXED64:
+ case fieldTypes.SFIXED64:
+ case fieldTypes.FHASH64:
+ return wireTypes.FIXED64;
+
+ case fieldTypes.STRING:
+ case fieldTypes.MESSAGE:
+ case fieldTypes.BYTES:
+ return wireTypes.DELIMITED;
+
+ case fieldTypes.FLOAT:
+ case fieldTypes.FIXED32:
+ case fieldTypes.SFIXED32:
+ return wireTypes.FIXED32;
+
+ case fieldTypes.INVALID:
+ case fieldTypes.GROUP:
+ default:
+ return wireTypes.INVALID;
+ }
+};
+
+
+/**
+ * Flag to indicate a missing field.
+ * @const {number}
+ */
+jspb.BinaryConstants.INVALID_FIELD_NUMBER = -1;
+
+
+/**
+ * The smallest denormal float32 value.
+ * @const {number}
+ */
+jspb.BinaryConstants.FLOAT32_EPS = 1.401298464324817e-45;
+
+
+/**
+ * The smallest normal float64 value.
+ * @const {number}
+ */
+jspb.BinaryConstants.FLOAT32_MIN = 1.1754943508222875e-38;
+
+
+/**
+ * The largest finite float32 value.
+ * @const {number}
+ */
+jspb.BinaryConstants.FLOAT32_MAX = 3.4028234663852886e+38;
+
+
+/**
+ * The smallest denormal float64 value.
+ * @const {number}
+ */
+jspb.BinaryConstants.FLOAT64_EPS = 5e-324;
+
+
+/**
+ * The smallest normal float64 value.
+ * @const {number}
+ */
+jspb.BinaryConstants.FLOAT64_MIN = 2.2250738585072014e-308;
+
+
+/**
+ * The largest finite float64 value.
+ * @const {number}
+ */
+jspb.BinaryConstants.FLOAT64_MAX = 1.7976931348623157e+308;
+
+
+/**
+ * Convenience constant equal to 2^20.
+ * @const {number}
+ */
+jspb.BinaryConstants.TWO_TO_20 = 1048576;
+
+
+/**
+ * Convenience constant equal to 2^23.
+ * @const {number}
+ */
+jspb.BinaryConstants.TWO_TO_23 = 8388608;
+
+
+/**
+ * Convenience constant equal to 2^31.
+ * @const {number}
+ */
+jspb.BinaryConstants.TWO_TO_31 = 2147483648;
+
+
+/**
+ * Convenience constant equal to 2^32.
+ * @const {number}
+ */
+jspb.BinaryConstants.TWO_TO_32 = 4294967296;
+
+
+/**
+ * Convenience constant equal to 2^52.
+ * @const {number}
+ */
+jspb.BinaryConstants.TWO_TO_52 = 4503599627370496;
+
+
+/**
+ * Convenience constant equal to 2^63.
+ * @const {number}
+ */
+jspb.BinaryConstants.TWO_TO_63 = 9223372036854775808;
+
+
+/**
+ * Convenience constant equal to 2^64.
+ * @const {number}
+ */
+jspb.BinaryConstants.TWO_TO_64 = 18446744073709551616;
+
+
+/**
+ * Eight-character string of zeros, used as the default 64-bit hash value.
+ * @const {string}
+ */
+jspb.BinaryConstants.ZERO_HASH = '\0\0\0\0\0\0\0\0';
