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diff --git a/comm/chat/modules/NormalizedMap.sys.mjs b/comm/chat/modules/NormalizedMap.sys.mjs
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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * A Map that automatically normalizes keys before accessing the values.
+ *
+ * The constructor takes two parameters:
+ *  aNormalize:   A function which takes a string and returns the "normalized"
+ *                version of it.
+ *  aIterable:    A iterable to prefill the map with, keys will be normalized.
+ *
+ * Returns a Map object that will automatically run aNormalize on any operations
+ * involving keys.
+ */
+export class NormalizedMap extends Map {
+  constructor(aNormalize, aIterable = []) {
+    if (typeof aNormalize != "function") {
+      throw new Error("NormalizedMap must have a normalize function!");
+    }
+    // Create the wrapped Map; use the provided iterable after normalizing the
+    // keys.
+    let entries = [...aIterable].map(([key, val]) => [aNormalize(key), val]);
+    super(entries);
+    // Note: In derived classes, super() must be called before using 'this'.
+    this._normalize = aNormalize;
+  }
+
+  // Dummy normalize function.
+  _normalize(aKey) {
+    return aKey;
+  }
+
+  // Anything that accepts a key as an input needs to be manually overridden.
+  delete(key) {
+    return super.delete(this._normalize(key));
+  }
+  get(key) {
+    return super.get(this._normalize(key));
+  }
+  has(key) {
+    return super.has(this._normalize(key));
+  }
+  set(key, val) {
+    super.set(this._normalize(key), val);
+    return this;
+  }
+}