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diff --git a/devtools/client/debugger/src/utils/shallow-equal.js b/devtools/client/debugger/src/utils/shallow-equal.js
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+++ b/devtools/client/debugger/src/utils/shallow-equal.js
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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/>. */
+
+/**
+ * Shallow equal will consider equal:
+ *  - exact same values (strict '===' equality)
+ *  - distinct array instances having the exact same values in them (same number and strict equality).
+ *  - distinct object instances having the exact same attributes and values.
+ *
+ * It will typically consider different array and object whose values
+ * aren't strictly equal. You may consider using "deep equality" checks for this scenario.
+ */
+export function shallowEqual(value, other) {
+  if (value === other) {
+    return true;
+  }
+
+  if (Array.isArray(value) && Array.isArray(other)) {
+    return arrayShallowEqual(value, other);
+  }
+
+  if (isObject(value) && isObject(other)) {
+    return objectShallowEqual(value, other);
+  }
+
+  return false;
+}
+
+export function arrayShallowEqual(value, other) {
+  // Redo this check in case we are called directly from the selectors.
+  if (value === other) {
+    return true;
+  }
+  return value.length === other.length && value.every((k, i) => k === other[i]);
+}
+
+function objectShallowEqual(value, other) {
+  const existingKeys = Object.keys(other);
+  const keys = Object.keys(value);
+
+  return (
+    keys.length === existingKeys.length &&
+    keys.every((k, i) => k === existingKeys[i]) &&
+    keys.every(k => value[k] === other[k])
+  );
+}
+
+function isObject(value) {
+  return typeof value === "object" && !!value;
+}