Add kill switch mechanism

This code implements the kill switch mechanism in the extension. This is
explained in //src/killSwitch/README.md and in the design doc:
https://docs.google.com/document/d/1O5YV6_WcxwrUyz-lwHOSTfZ3oyIFWj2EQee0VuKkhaA/edit.

Bug: twpowertools:64

Change-Id: Ia993c78035bba7038aafd53d156f20954217e86f
diff --git a/src/third_party/google-protobuf-commonjs_strict/google/protobuf/timestamp_pb.js b/src/third_party/google-protobuf-commonjs_strict/google/protobuf/timestamp_pb.js
new file mode 100644
index 0000000..42ece50
--- /dev/null
+++ b/src/third_party/google-protobuf-commonjs_strict/google/protobuf/timestamp_pb.js
@@ -0,0 +1,236 @@
+// source: google/protobuf/timestamp.proto
+/**
+ * @fileoverview
+ * @enhanceable
+ * @suppress {missingRequire} reports error on implicit type usages.
+ * @suppress {messageConventions} JS Compiler reports an error if a variable or
+ *     field starts with 'MSG_' and isn't a translatable message.
+ * @public
+ */
+// GENERATED CODE -- DO NOT EDIT!
+/* eslint-disable */
+// @ts-nocheck
+
+var jspb = require('google-protobuf');
+var goog = jspb;
+var proto = {};
+
+goog.exportSymbol('google.protobuf.Timestamp', null, proto);
+/**
+ * Generated by JsPbCodeGenerator.
+ * @param {Array=} opt_data Optional initial data array, typically from a
+ * server response, or constructed directly in Javascript. The array is used
+ * in place and becomes part of the constructed object. It is not cloned.
+ * If no data is provided, the constructed object will be empty, but still
+ * valid.
+ * @extends {jspb.Message}
+ * @constructor
+ */
+proto.google.protobuf.Timestamp = function(opt_data) {
+  jspb.Message.initialize(this, opt_data, 0, -1, null, null);
+};
+goog.inherits(proto.google.protobuf.Timestamp, jspb.Message);
+if (goog.DEBUG && !COMPILED) {
+  /**
+   * @public
+   * @override
+   */
+  proto.google.protobuf.Timestamp.displayName = 'proto.google.protobuf.Timestamp';
+}
+
+
+
+if (jspb.Message.GENERATE_TO_OBJECT) {
+/**
+ * Creates an object representation of this proto.
+ * Field names that are reserved in JavaScript and will be renamed to pb_name.
+ * Optional fields that are not set will be set to undefined.
+ * To access a reserved field use, foo.pb_<name>, eg, foo.pb_default.
+ * For the list of reserved names please see:
+ *     net/proto2/compiler/js/internal/generator.cc#kKeyword.
+ * @param {boolean=} opt_includeInstance Deprecated. whether to include the
+ *     JSPB instance for transitional soy proto support:
+ *     http://goto/soy-param-migration
+ * @return {!Object}
+ */
+proto.google.protobuf.Timestamp.prototype.toObject = function(opt_includeInstance) {
+  return proto.google.protobuf.Timestamp.toObject(opt_includeInstance, this);
+};
+
+
+/**
+ * Static version of the {@see toObject} method.
+ * @param {boolean|undefined} includeInstance Deprecated. Whether to include
+ *     the JSPB instance for transitional soy proto support:
+ *     http://goto/soy-param-migration
+ * @param {!proto.google.protobuf.Timestamp} msg The msg instance to transform.
+ * @return {!Object}
+ * @suppress {unusedLocalVariables} f is only used for nested messages
+ */
+proto.google.protobuf.Timestamp.toObject = function(includeInstance, msg) {
+  var f, obj = {
+    seconds: jspb.Message.getFieldWithDefault(msg, 1, 0),
+    nanos: jspb.Message.getFieldWithDefault(msg, 2, 0)
+  };
+
+  if (includeInstance) {
+    obj.$jspbMessageInstance = msg;
+  }
+  return obj;
+};
+}
+
+
+/**
+ * Deserializes binary data (in protobuf wire format).
+ * @param {jspb.ByteSource} bytes The bytes to deserialize.
+ * @return {!proto.google.protobuf.Timestamp}
+ */
+proto.google.protobuf.Timestamp.deserializeBinary = function(bytes) {
+  var reader = new jspb.BinaryReader(bytes);
+  var msg = new proto.google.protobuf.Timestamp;
+  return proto.google.protobuf.Timestamp.deserializeBinaryFromReader(msg, reader);
+};
+
+
+/**
+ * Deserializes binary data (in protobuf wire format) from the
+ * given reader into the given message object.
+ * @param {!proto.google.protobuf.Timestamp} msg The message object to deserialize into.
+ * @param {!jspb.BinaryReader} reader The BinaryReader to use.
+ * @return {!proto.google.protobuf.Timestamp}
+ */
+proto.google.protobuf.Timestamp.deserializeBinaryFromReader = function(msg, reader) {
+  while (reader.nextField()) {
+    if (reader.isEndGroup()) {
+      break;
+    }
+    var field = reader.getFieldNumber();
+    switch (field) {
+    case 1:
+      var value = /** @type {number} */ (reader.readInt64());
+      msg.setSeconds(value);
+      break;
+    case 2:
+      var value = /** @type {number} */ (reader.readInt32());
+      msg.setNanos(value);
+      break;
+    default:
+      reader.skipField();
+      break;
+    }
+  }
+  return msg;
+};
+
+
+/**
+ * Serializes the message to binary data (in protobuf wire format).
+ * @return {!Uint8Array}
+ */
+proto.google.protobuf.Timestamp.prototype.serializeBinary = function() {
+  var writer = new jspb.BinaryWriter();
+  proto.google.protobuf.Timestamp.serializeBinaryToWriter(this, writer);
+  return writer.getResultBuffer();
+};
+
+
+/**
+ * Serializes the given message to binary data (in protobuf wire
+ * format), writing to the given BinaryWriter.
+ * @param {!proto.google.protobuf.Timestamp} message
+ * @param {!jspb.BinaryWriter} writer
+ * @suppress {unusedLocalVariables} f is only used for nested messages
+ */
+proto.google.protobuf.Timestamp.serializeBinaryToWriter = function(message, writer) {
+  var f = undefined;
+  f = message.getSeconds();
+  if (f !== 0) {
+    writer.writeInt64(
+      1,
+      f
+    );
+  }
+  f = message.getNanos();
+  if (f !== 0) {
+    writer.writeInt32(
+      2,
+      f
+    );
+  }
+};
+
+
+/**
+ * optional int64 seconds = 1;
+ * @return {number}
+ */
+proto.google.protobuf.Timestamp.prototype.getSeconds = function() {
+  return /** @type {number} */ (jspb.Message.getFieldWithDefault(this, 1, 0));
+};
+
+
+/**
+ * @param {number} value
+ * @return {!proto.google.protobuf.Timestamp} returns this
+ */
+proto.google.protobuf.Timestamp.prototype.setSeconds = function(value) {
+  return jspb.Message.setProto3IntField(this, 1, value);
+};
+
+
+/**
+ * optional int32 nanos = 2;
+ * @return {number}
+ */
+proto.google.protobuf.Timestamp.prototype.getNanos = function() {
+  return /** @type {number} */ (jspb.Message.getFieldWithDefault(this, 2, 0));
+};
+
+
+/**
+ * @param {number} value
+ * @return {!proto.google.protobuf.Timestamp} returns this
+ */
+proto.google.protobuf.Timestamp.prototype.setNanos = function(value) {
+  return jspb.Message.setProto3IntField(this, 2, value);
+};
+
+
+goog.object.extend(exports, proto);
+/* This code will be inserted into generated code for
+ * google/protobuf/timestamp.proto. */
+
+/**
+ * Returns a JavaScript 'Date' object corresponding to this Timestamp.
+ * @return {!Date}
+ */
+proto.google.protobuf.Timestamp.prototype.toDate = function() {
+  var seconds = this.getSeconds();
+  var nanos = this.getNanos();
+
+  return new Date((seconds * 1000) + (nanos / 1000000));
+};
+
+
+/**
+ * Sets the value of this Timestamp object to be the given Date.
+ * @param {!Date} value The value to set.
+ */
+proto.google.protobuf.Timestamp.prototype.fromDate = function(value) {
+  this.setSeconds(Math.floor(value.getTime() / 1000));
+  this.setNanos(value.getMilliseconds() * 1000000);
+};
+
+
+/**
+ * Factory method that returns a Timestamp object with value equal to
+ * the given Date.
+ * @param {!Date} value The value to set.
+ * @return {!proto.google.protobuf.Timestamp}
+ */
+proto.google.protobuf.Timestamp.fromDate = function(value) {
+  var timestamp = new proto.google.protobuf.Timestamp();
+  timestamp.fromDate(value);
+  return timestamp;
+};