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diff --git a/browser/components/installerprefs/InstallerPrefs.sys.mjs b/browser/components/installerprefs/InstallerPrefs.sys.mjs
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+++ b/browser/components/installerprefs/InstallerPrefs.sys.mjs
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+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* 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/. */
+
+/**
+ * The installer prefs component provides a way to get a specific set of prefs
+ * from a profile into a place where the installer can read them. The primary
+ * reason for wanting to do this is so we can run things like Shield studies
+ * on installer features; normally those are enabled by setting a pref, but
+ * the installer runs outside of any profile and so has no access to prefs.
+ * So we need to do something else to allow it to read these prefs.
+ *
+ * The mechanism we use here is to reflect the values of a list of relevant
+ * prefs into registry values. One registry value is created for each pref
+ * that is set. Each installation of the product gets its own registry key
+ * (based on the path hash). This is obviously a somewhat wider scope than a
+ * single profile, but it should be close enough in enough cases to suit our
+ * purposes here.
+ *
+ * Currently this module only supports bool prefs. Other types could likely
+ * be added if needed, but it doesn't seem necessary for the primary use case.
+ */
+
+// All prefs processed through this component must be in this branch.
+const INSTALLER_PREFS_BRANCH = "installer.";
+
+// This is the list of prefs that will be reflected to the registry. It should
+// be kept up to date so that it reflects the list of prefs that are in
+// current use (e.g., currently active experiments).
+// Only add prefs to this list which are in INSTALLER_PREFS_BRANCH;
+// any others will be ignored.
+const INSTALLER_PREFS_LIST = ["installer.taskbarpin.win10.enabled"];
+
+import { AppConstants } from "resource://gre/modules/AppConstants.sys.mjs";
+import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
+
+// This constructor can take a list of prefs to override the default one,
+// but this is really only intended for tests to use. Normal usage should be
+// to leave the parameter omitted/undefined.
+export function InstallerPrefs(prefsList) {
+  this.prefsList = prefsList || INSTALLER_PREFS_LIST;
+
+  // Each pref to be reflected will get a value created under this key, in HKCU.
+  // The path will look something like:
+  // "Software\Mozilla\Firefox\Installer\71AE18FE3142402B\".
+  XPCOMUtils.defineLazyGetter(this, "_registryKeyPath", function () {
+    const app = AppConstants.MOZ_APP_NAME;
+    const vendor = Services.appinfo.vendor || "Mozilla";
+    const xreDirProvider = Cc[
+      "@mozilla.org/xre/directory-provider;1"
+    ].getService(Ci.nsIXREDirProvider);
+    const installHash = xreDirProvider.getInstallHash();
+    return `Software\\${vendor}\\${app}\\Installer\\${installHash}`;
+  });
+}
+
+InstallerPrefs.prototype = {
+  classID: Components.ID("{cd8a6995-1f19-4cdd-9ed1-d6263302f594}"),
+  contractID: "@mozilla.org/installerprefs;1",
+
+  QueryInterface: ChromeUtils.generateQI(["nsIObserver"]),
+
+  observe(subject, topic, data) {
+    switch (topic) {
+      case "profile-after-change": {
+        if (
+          AppConstants.platform != "win" ||
+          !this.prefsList ||
+          !this.prefsList.length
+        ) {
+          // This module has no work to do.
+          break;
+        }
+        const regKey = this._openRegKey();
+        this._reflectPrefsToRegistry(regKey);
+        this._registerPrefListeners();
+        regKey.close();
+        break;
+      }
+      case "nsPref:changed": {
+        const regKey = this._openRegKey();
+        if (this.prefsList.includes(data)) {
+          this._reflectOnePrefToRegistry(regKey, data);
+        }
+        regKey.close();
+        break;
+      }
+    }
+  },
+
+  _registerPrefListeners() {
+    Services.prefs.addObserver(INSTALLER_PREFS_BRANCH, this);
+  },
+
+  _cleanRegistryKey(regKey) {
+    for (let i = regKey.valueCount - 1; i >= 0; --i) {
+      const name = regKey.getValueName(i);
+      if (name.startsWith(INSTALLER_PREFS_BRANCH)) {
+        regKey.removeValue(name);
+      }
+    }
+  },
+
+  _reflectPrefsToRegistry(regKey) {
+    this._cleanRegistryKey(regKey);
+    this.prefsList.forEach(pref =>
+      this._reflectOnePrefToRegistry(regKey, pref)
+    );
+  },
+
+  _reflectOnePrefToRegistry(regKey, pref) {
+    if (!pref.startsWith(INSTALLER_PREFS_BRANCH)) {
+      return;
+    }
+
+    const value = Services.prefs.getBoolPref(pref, false);
+    if (value) {
+      regKey.writeIntValue(pref, 1);
+    } else {
+      try {
+        regKey.removeValue(pref);
+      } catch (ex) {
+        // This removeValue call is prone to failing because the value we
+        // tried to remove didn't exist. Obviously that isn't really an error
+        // that we need to handle.
+      }
+    }
+  },
+
+  _openRegKey() {
+    const key = Cc["@mozilla.org/windows-registry-key;1"].createInstance(
+      Ci.nsIWindowsRegKey
+    );
+    key.create(
+      key.ROOT_KEY_CURRENT_USER,
+      this._registryKeyPath,
+      key.ACCESS_READ | key.ACCESS_WRITE | key.WOW64_64
+    );
+    return key;
+  },
+};