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diff --git a/node_modules/workbox-broadcast-cache-update/BroadcastCacheUpdate.mjs b/node_modules/workbox-broadcast-cache-update/BroadcastCacheUpdate.mjs
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+/*
+ Copyright 2016 Google Inc. All Rights Reserved.
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+*/
+
+import {WorkboxError} from 'workbox-core/_private/WorkboxError.mjs';
+import {responsesAreSame} from './utils/responsesAreSame.mjs';
+import {broadcastUpdate} from './broadcastUpdate.mjs';
+import './_version.mjs';
+
+/**
+ * Uses the [Broadcast Channel API]{@link https://developers.google.com/web/updates/2016/09/broadcastchannel}
+ * to notify interested parties when a cached response has been updated.
+ *
+ * For efficiency's sake, the underlying response bodies are not compared;
+ * only specific response headers are checked.
+ *
+ * @memberof workbox.broadcastUpdate
+ */
+class BroadcastCacheUpdate {
+  /**
+   * Construct a BroadcastCacheUpdate instance with a specific `channelName` to
+   * broadcast messages on
+   *
+   * @param {string} channelName The name that will be used when creating
+   * the `BroadcastChannel`.
+   * @param {Object} options
+   * @param {Array<string>}
+   * [options.headersToCheck=['content-length', 'etag', 'last-modified']] A
+   * list of headers that will be used to determine whether the responses
+   * differ.
+   * @param {string} [options.source='workbox-broadcast-cache-update'] An
+   * attribution value that indicates where the update originated.
+   */
+  constructor(channelName, {headersToCheck, source} = {}) {
+    if (process.env.NODE_ENV !== 'production') {
+      if (typeof channelName !== 'string' || channelName.length === 0) {
+        throw new WorkboxError('channel-name-required');
+      }
+    }
+
+    this._channelName = channelName;
+    this._headersToCheck = headersToCheck || [
+      'content-length',
+      'etag',
+      'last-modified',
+    ];
+    this._source = source || 'workbox-broadcast-cache-update';
+
+    // TODO assert typeof headersToCheck instanceof Array
+  }
+
+  /**
+   * @return {BroadcastChannel|undefined} The BroadcastChannel instance used for
+   * broadcasting updates, or undefined if the browser doesn't support the
+   * Broadcast Channel API.
+   *
+   * @private
+   */
+  _getChannel() {
+    if (('BroadcastChannel' in self) && !this._channel) {
+      this._channel = new BroadcastChannel(this._channelName);
+    }
+    return this._channel;
+  }
+
+  /**
+   * Compare two [Responses](https://developer.mozilla.org/en-US/docs/Web/API/Response)
+   * and send a message via the
+   * {@link https://developers.google.com/web/updates/2016/09/broadcastchannel|Broadcast Channel API}
+   * if they differ.
+   *
+   * Neither of the Responses can be {@link http://stackoverflow.com/questions/39109789|opaque}.
+   *
+   * @param {Response} firstResponse First responses to compare.
+   * @param {Response} secondResponse Second responses to compare.
+   * @param {string} url The URL of the updated request.
+   * @param {string} cacheName Name of the cache the responses belong to.
+   * This is included in the message posted on the broadcast channel.
+   */
+  notifyIfUpdated(firstResponse, secondResponse, url, cacheName) {
+    if (!responsesAreSame(
+      firstResponse, secondResponse, this._headersToCheck)) {
+      broadcastUpdate(this._getChannel(), cacheName, url, this._source);
+    }
+  }
+}
+
+export {BroadcastCacheUpdate};