Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 737 insertions, 0 deletions

diff --git a/browser/base/content/browser-fullZoom.js b/browser/base/content/browser-fullZoom.js
new file mode 100644
index 0000000000..7790df3f41
--- /dev/null
+++ b/browser/base/content/browser-fullZoom.js
@@ -0,0 +1,737 @@
+/* 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/. */
+
+// This file is loaded into the browser window scope.
+/* eslint-env mozilla/browser-window */
+
+/**
+ * Controls the "full zoom" setting and its site-specific preferences.
+ */
+var FullZoom = {
+  // Identifies the setting in the content prefs database.
+  name: "browser.content.full-zoom",
+
+  // browser.zoom.siteSpecific preference cache
+  _siteSpecificPref: undefined,
+
+  // browser.zoom.updateBackgroundTabs preference cache
+  updateBackgroundTabs: undefined,
+
+  // This maps the browser to monotonically increasing integer
+  // tokens. _browserTokenMap[browser] is increased each time the zoom is
+  // changed in the browser. See _getBrowserToken and _ignorePendingZoomAccesses.
+  _browserTokenMap: new WeakMap(),
+
+  // Stores initial locations if we receive onLocationChange
+  // events before we're initialized.
+  _initialLocations: new WeakMap(),
+
+  get siteSpecific() {
+    if (this._siteSpecificPref === undefined) {
+      this._siteSpecificPref = Services.prefs.getBoolPref(
+        "browser.zoom.siteSpecific"
+      );
+    }
+    return this._siteSpecificPref;
+  },
+
+  // nsISupports
+
+  QueryInterface: ChromeUtils.generateQI([
+    "nsIObserver",
+    "nsIContentPrefObserver",
+    "nsISupportsWeakReference",
+  ]),
+
+  // Initialization & Destruction
+
+  init: function FullZoom_init() {
+    gBrowser.addEventListener("DoZoomEnlargeBy10", this);
+    gBrowser.addEventListener("DoZoomReduceBy10", this);
+    window.addEventListener("MozScaleGestureComplete", this);
+
+    // Register ourselves with the service so we know when our pref changes.
+    this._cps2 = Cc["@mozilla.org/content-pref/service;1"].getService(
+      Ci.nsIContentPrefService2
+    );
+    this._cps2.addObserverForName(this.name, this);
+
+    this.updateBackgroundTabs = Services.prefs.getBoolPref(
+      "browser.zoom.updateBackgroundTabs"
+    );
+
+    // Listen for changes to the browser.zoom branch so we can enable/disable
+    // updating background tabs and per-site saving and restoring of zoom levels.
+    Services.prefs.addObserver("browser.zoom.", this, true);
+
+    // If we received onLocationChange events for any of the current browsers
+    // before we were initialized we want to replay those upon initialization.
+    for (let browser of gBrowser.browsers) {
+      if (this._initialLocations.has(browser)) {
+        this.onLocationChange(...this._initialLocations.get(browser), browser);
+      }
+    }
+
+    // This should be nulled after initialization.
+    this._initialLocations = null;
+  },
+
+  destroy: function FullZoom_destroy() {
+    Services.prefs.removeObserver("browser.zoom.", this);
+    this._cps2.removeObserverForName(this.name, this);
+    gBrowser.removeEventListener("DoZoomEnlargeBy10", this);
+    gBrowser.removeEventListener("DoZoomReduceBy10", this);
+    window.removeEventListener("MozScaleGestureComplete", this);
+  },
+
+  // Event Handlers
+
+  // EventListener
+
+  handleEvent: function FullZoom_handleEvent(event) {
+    switch (event.type) {
+      case "DoZoomEnlargeBy10":
+        this.changeZoomBy(this._getTargetedBrowser(event), 0.1);
+        break;
+      case "DoZoomReduceBy10":
+        this.changeZoomBy(this._getTargetedBrowser(event), -0.1);
+        break;
+      case "MozScaleGestureComplete": {
+        let nonDefaultScalingZoom = event.detail != 1.0;
+        this.updateCommands(nonDefaultScalingZoom);
+        break;
+      }
+    }
+  },
+
+  // nsIObserver
+
+  observe(aSubject, aTopic, aData) {
+    switch (aTopic) {
+      case "nsPref:changed":
+        switch (aData) {
+          case "browser.zoom.siteSpecific":
+            // Invalidate pref cache.
+            this._siteSpecificPref = undefined;
+            break;
+          case "browser.zoom.updateBackgroundTabs":
+            this.updateBackgroundTabs = Services.prefs.getBoolPref(
+              "browser.zoom.updateBackgroundTabs"
+            );
+            break;
+          case "browser.zoom.full": {
+            this.updateCommands();
+            break;
+          }
+        }
+        break;
+    }
+  },
+
+  // nsIContentPrefObserver
+
+  onContentPrefSet: function FullZoom_onContentPrefSet(
+    aGroup,
+    aName,
+    aValue,
+    aIsPrivate
+  ) {
+    this._onContentPrefChanged(aGroup, aValue, aIsPrivate);
+  },
+
+  onContentPrefRemoved: function FullZoom_onContentPrefRemoved(
+    aGroup,
+    aName,
+    aIsPrivate
+  ) {
+    this._onContentPrefChanged(aGroup, undefined, aIsPrivate);
+  },
+
+  /**
+   * Appropriately updates the zoom level after a content preference has
+   * changed.
+   *
+   * @param aGroup  The group of the changed preference.
+   * @param aValue  The new value of the changed preference.  Pass undefined to
+   *                indicate the preference's removal.
+   */
+  _onContentPrefChanged: function FullZoom__onContentPrefChanged(
+    aGroup,
+    aValue,
+    aIsPrivate
+  ) {
+    if (this._isNextContentPrefChangeInternal) {
+      // Ignore changes that FullZoom itself makes.  This works because the
+      // content pref service calls callbacks before notifying observers, and it
+      // does both in the same turn of the event loop.
+      delete this._isNextContentPrefChangeInternal;
+      return;
+    }
+
+    let browser = gBrowser.selectedBrowser;
+    if (!browser.currentURI) {
+      return;
+    }
+
+    if (this._isPDFViewer(browser)) {
+      return;
+    }
+
+    let ctxt = this._loadContextFromBrowser(browser);
+    let domain = this._cps2.extractDomain(browser.currentURI.spec);
+    if (aGroup) {
+      if (aGroup == domain && ctxt.usePrivateBrowsing == aIsPrivate) {
+        this._applyPrefToZoom(aValue, browser);
+      }
+      return;
+    }
+
+    // If the current page doesn't have a site-specific preference, then its
+    // zoom should be set to the new global preference now that the global
+    // preference has changed.
+    let hasPref = false;
+    let token = this._getBrowserToken(browser);
+    this._cps2.getByDomainAndName(browser.currentURI.spec, this.name, ctxt, {
+      handleResult() {
+        hasPref = true;
+      },
+      handleCompletion: () => {
+        if (!hasPref && token.isCurrent) {
+          this._applyPrefToZoom(undefined, browser);
+        }
+      },
+    });
+  },
+
+  // location change observer
+
+  /**
+   * Called when the location of a tab changes.
+   * When that happens, we need to update the current zoom level if appropriate.
+   *
+   * @param aURI
+   *        A URI object representing the new location.
+   * @param aIsTabSwitch
+   *        Whether this location change has happened because of a tab switch.
+   * @param aBrowser
+   *        (optional) browser object displaying the document
+   */
+  onLocationChange: function FullZoom_onLocationChange(
+    aURI,
+    aIsTabSwitch,
+    aBrowser
+  ) {
+    let browser = aBrowser || gBrowser.selectedBrowser;
+
+    // If we haven't been initialized yet but receive an onLocationChange
+    // notification then let's store and replay it upon initialization.
+    if (this._initialLocations) {
+      this._initialLocations.set(browser, [aURI, aIsTabSwitch]);
+      return;
+    }
+
+    // Ignore all pending async zoom accesses in the browser.  Pending accesses
+    // that started before the location change will be prevented from applying
+    // to the new location.
+    this._ignorePendingZoomAccesses(browser);
+
+    if (!aURI || (aIsTabSwitch && !this._isSiteSpecific(browser))) {
+      this._notifyOnLocationChange(browser);
+      return;
+    }
+
+    if (aURI.spec == "about:blank") {
+      if (
+        !browser.contentPrincipal ||
+        browser.contentPrincipal.isNullPrincipal
+      ) {
+        // For an about:blank with a null principal, zooming any amount does not
+        // make any sense - so simply do 100%.
+        this._applyPrefToZoom(
+          1,
+          browser,
+          this._notifyOnLocationChange.bind(this, browser)
+        );
+      } else {
+        // If it's not a null principal, there may be content loaded into it,
+        // so use the global pref. This will avoid a cps2 roundtrip if we've
+        // already loaded the global pref once. Really, this should probably
+        // use the contentPrincipal's origin if it's an http(s) principal.
+        // (See bug 1457597)
+        this._applyPrefToZoom(
+          undefined,
+          browser,
+          this._notifyOnLocationChange.bind(this, browser)
+        );
+      }
+      return;
+    }
+
+    // Media documents should always start at 1, and are not affected by prefs.
+    if (!aIsTabSwitch && browser.isSyntheticDocument) {
+      ZoomManager.setZoomForBrowser(browser, 1);
+      // _ignorePendingZoomAccesses already called above, so no need here.
+      this._notifyOnLocationChange(browser);
+      return;
+    }
+
+    // The PDF viewer zooming isn't handled by `ZoomManager`, ensure that the
+    // browser zoom level always gets reset to 100% on load (to prevent the
+    // UI elements of the PDF viewer from being zoomed in/out on load).
+    if (this._isPDFViewer(browser)) {
+      this._applyPrefToZoom(
+        1,
+        browser,
+        this._notifyOnLocationChange.bind(this, browser)
+      );
+      return;
+    }
+
+    // See if the zoom pref is cached.
+    let ctxt = this._loadContextFromBrowser(browser);
+    let pref = this._cps2.getCachedByDomainAndName(aURI.spec, this.name, ctxt);
+    if (pref) {
+      this._applyPrefToZoom(
+        pref.value,
+        browser,
+        this._notifyOnLocationChange.bind(this, browser)
+      );
+      return;
+    }
+
+    // It's not cached, so we have to asynchronously fetch it.
+    let value = undefined;
+    let token = this._getBrowserToken(browser);
+    this._cps2.getByDomainAndName(aURI.spec, this.name, ctxt, {
+      handleResult(resultPref) {
+        value = resultPref.value;
+      },
+      handleCompletion: () => {
+        if (!token.isCurrent) {
+          this._notifyOnLocationChange(browser);
+          return;
+        }
+        this._applyPrefToZoom(
+          value,
+          browser,
+          this._notifyOnLocationChange.bind(this, browser)
+        );
+      },
+    });
+  },
+
+  // update state of zoom menu items
+
+  /**
+   * Updates the current windows Zoom commands for zooming in, zooming out
+   * and resetting the zoom level.
+   *
+   * @param {boolean} [forceResetEnabled=false]
+   *   Set to true if the zoom reset command should be enabled regardless of
+   *   whether or not the ZoomManager.zoom level is at 1.0. This is specifically
+   *   for when using scaling zoom via the pinch gesture which doesn't cause
+   *   the ZoomManager.zoom level to change.
+   * @returns Promise
+   * @resolves undefined
+   */
+  updateCommands: async function FullZoom_updateCommands(
+    forceResetEnabled = false
+  ) {
+    let zoomLevel = ZoomManager.zoom;
+    let defaultZoomLevel = await ZoomUI.getGlobalValue();
+    let reduceCmd = document.getElementById("cmd_fullZoomReduce");
+    if (zoomLevel == ZoomManager.MIN) {
+      reduceCmd.setAttribute("disabled", "true");
+    } else {
+      reduceCmd.removeAttribute("disabled");
+    }
+
+    let enlargeCmd = document.getElementById("cmd_fullZoomEnlarge");
+    if (zoomLevel == ZoomManager.MAX) {
+      enlargeCmd.setAttribute("disabled", "true");
+    } else {
+      enlargeCmd.removeAttribute("disabled");
+    }
+
+    let resetCmd = document.getElementById("cmd_fullZoomReset");
+    if (zoomLevel == defaultZoomLevel && !forceResetEnabled) {
+      resetCmd.setAttribute("disabled", "true");
+    } else {
+      resetCmd.removeAttribute("disabled");
+    }
+
+    let fullZoomCmd = document.getElementById("cmd_fullZoomToggle");
+    if (!ZoomManager.useFullZoom) {
+      fullZoomCmd.setAttribute("checked", "true");
+    } else {
+      fullZoomCmd.setAttribute("checked", "false");
+    }
+  },
+
+  // Setting & Pref Manipulation
+
+  sendMessageToPDFViewer(browser, name) {
+    try {
+      browser.sendMessageToActor(name, {}, "Pdfjs");
+    } catch (ex) {
+      console.error(ex);
+    }
+  },
+
+  /**
+   * If browser in reader mode sends message to reader in order to decrease font size,
+   * Otherwise reduces the zoom level of the page in the current browser.
+   */
+  async reduce() {
+    let browser = gBrowser.selectedBrowser;
+    if (browser.currentURI.spec.startsWith("about:reader")) {
+      browser.sendMessageToActor("Reader:ZoomOut", {}, "AboutReader");
+    } else if (this._isPDFViewer(browser)) {
+      this.sendMessageToPDFViewer(browser, "PDFJS:ZoomOut");
+    } else {
+      ZoomManager.reduce();
+      this._ignorePendingZoomAccesses(browser);
+      await this._applyZoomToPref(browser);
+    }
+  },
+
+  /**
+   * If browser in reader mode sends message to reader in order to increase font size,
+   * Otherwise enlarges the zoom level of the page in the current browser.
+   */
+  async enlarge() {
+    let browser = gBrowser.selectedBrowser;
+    if (browser.currentURI.spec.startsWith("about:reader")) {
+      browser.sendMessageToActor("Reader:ZoomIn", {}, "AboutReader");
+    } else if (this._isPDFViewer(browser)) {
+      this.sendMessageToPDFViewer(browser, "PDFJS:ZoomIn");
+    } else {
+      ZoomManager.enlarge();
+      this._ignorePendingZoomAccesses(browser);
+      await this._applyZoomToPref(browser);
+    }
+  },
+
+  /**
+   * If browser in reader mode sends message to reader in order to increase font size,
+   * Otherwise enlarges the zoom level of the page in the current browser.
+   * This function is not async like reduce/enlarge, because it is invoked by our
+   * event handler. This means that the call to _applyZoomToPref is not awaited and
+   * will happen asynchronously.
+   */
+  changeZoomBy(aBrowser, aValue) {
+    if (aBrowser.currentURI.spec.startsWith("about:reader")) {
+      const message = aValue > 0 ? "Reader::ZoomIn" : "Reader:ZoomOut";
+      aBrowser.sendMessageToActor(message, {}, "AboutReader");
+      return;
+    } else if (this._isPDFViewer(aBrowser)) {
+      const message = aValue > 0 ? "PDFJS::ZoomIn" : "PDFJS:ZoomOut";
+      this.sendMessageToPDFViewer(aBrowser, message);
+      return;
+    }
+    let zoom = ZoomManager.getZoomForBrowser(aBrowser);
+    zoom += aValue;
+    if (zoom < ZoomManager.MIN) {
+      zoom = ZoomManager.MIN;
+    } else if (zoom > ZoomManager.MAX) {
+      zoom = ZoomManager.MAX;
+    }
+    ZoomManager.setZoomForBrowser(aBrowser, zoom);
+    this._ignorePendingZoomAccesses(aBrowser);
+    this._applyZoomToPref(aBrowser);
+  },
+
+  /**
+   * Sets the zoom level for the given browser to the given floating
+   * point value, where 1 is the default zoom level.
+   */
+  setZoom(value, browser = gBrowser.selectedBrowser) {
+    if (this._isPDFViewer(browser)) {
+      return;
+    }
+    ZoomManager.setZoomForBrowser(browser, value);
+    this._ignorePendingZoomAccesses(browser);
+    this._applyZoomToPref(browser);
+  },
+
+  /**
+   * Sets the zoom level of the page in the given browser to the global zoom
+   * level.
+   *
+   * @return A promise which resolves when the zoom reset has been applied.
+   */
+  reset: function FullZoom_reset(browser = gBrowser.selectedBrowser) {
+    let forceValue;
+    if (browser.currentURI.spec.startsWith("about:reader")) {
+      browser.sendMessageToActor("Reader:ResetZoom", {}, "AboutReader");
+    } else if (this._isPDFViewer(browser)) {
+      this.sendMessageToPDFViewer(browser, "PDFJS:ZoomReset");
+      // Ensure that the UI elements of the PDF viewer won't be zoomed in/out
+      // on reset, even if/when browser default zoom value is not set to 100%.
+      forceValue = 1;
+    }
+    let token = this._getBrowserToken(browser);
+    let result = ZoomUI.getGlobalValue().then(value => {
+      if (token.isCurrent) {
+        ZoomManager.setZoomForBrowser(browser, forceValue || value);
+        this._ignorePendingZoomAccesses(browser);
+      }
+    });
+    this._removePref(browser);
+    return result;
+  },
+
+  resetScalingZoom: function FullZoom_resetScaling(
+    browser = gBrowser.selectedBrowser
+  ) {
+    browser.browsingContext?.resetScalingZoom();
+  },
+
+  /**
+   * Set the zoom level for a given browser.
+   *
+   * Per nsPresContext::setFullZoom, we can set the zoom to its current value
+   * without significant impact on performance, as the setting is only applied
+   * if it differs from the current setting.  In fact getting the zoom and then
+   * checking ourselves if it differs costs more.
+   *
+   * And perhaps we should always set the zoom even if it was more expensive,
+   * since nsDocumentViewer::SetTextZoom claims that child documents can have
+   * a different text zoom (although it would be unusual), and it implies that
+   * those child text zooms should get updated when the parent zoom gets set,
+   * and perhaps the same is true for full zoom
+   * (although nsDocumentViewer::SetFullZoom doesn't mention it).
+   *
+   * So when we apply new zoom values to the browser, we simply set the zoom.
+   * We don't check first to see if the new value is the same as the current
+   * one.
+   *
+   * @param aValue     The zoom level value.
+   * @param aBrowser   The zoom is set in this browser.  Required.
+   * @param aCallback  If given, it's asynchronously called when complete.
+   */
+  _applyPrefToZoom: function FullZoom__applyPrefToZoom(
+    aValue,
+    aBrowser,
+    aCallback
+  ) {
+    // The browser is sometimes half-destroyed because this method is called
+    // by content pref service callbacks, which themselves can be called at any
+    // time, even after browsers are closed.
+    if (
+      !aBrowser.mInitialized ||
+      aBrowser.isSyntheticDocument ||
+      (!this._isSiteSpecific(aBrowser) && aBrowser.tabHasCustomZoom)
+    ) {
+      this._executeSoon(aCallback);
+      return;
+    }
+
+    if (aValue !== undefined && this._isSiteSpecific(aBrowser)) {
+      ZoomManager.setZoomForBrowser(aBrowser, this._ensureValid(aValue));
+      this._ignorePendingZoomAccesses(aBrowser);
+      this._executeSoon(aCallback);
+      return;
+    }
+
+    // Above, we check if site-specific zoom is enabled before setting
+    // the tab browser zoom, however global zoom should work independent
+    // of the site-specific pref, so we do no checks here.
+    let token = this._getBrowserToken(aBrowser);
+    ZoomUI.getGlobalValue().then(value => {
+      if (token.isCurrent) {
+        ZoomManager.setZoomForBrowser(aBrowser, value);
+        this._ignorePendingZoomAccesses(aBrowser);
+      }
+      this._executeSoon(aCallback);
+    });
+  },
+
+  /**
+   * Saves the zoom level of the page in the given browser to the content
+   * prefs store.
+   *
+   * @param browser  The zoom of this browser will be saved.  Required.
+   */
+  _applyZoomToPref: function FullZoom__applyZoomToPref(browser) {
+    if (!this._isSiteSpecific(browser) || browser.isSyntheticDocument) {
+      // If site-specific zoom is disabled, we have called this function
+      // to adjust our tab's zoom level. It is now considered "custom"
+      // and we mark that here.
+      browser.tabHasCustomZoom = !this._isSiteSpecific(browser);
+      return null;
+    }
+
+    return new Promise(resolve => {
+      this._cps2.set(
+        browser.currentURI.spec,
+        this.name,
+        ZoomManager.getZoomForBrowser(browser),
+        this._loadContextFromBrowser(browser),
+        {
+          handleCompletion: () => {
+            this._isNextContentPrefChangeInternal = true;
+            resolve();
+          },
+        }
+      );
+    });
+  },
+
+  /**
+   * Removes from the content prefs store the zoom level of the given browser.
+   *
+   * @param browser  The zoom of this browser will be removed.  Required.
+   */
+  _removePref: function FullZoom__removePref(browser) {
+    if (browser.isSyntheticDocument) {
+      return;
+    }
+    let ctxt = this._loadContextFromBrowser(browser);
+    this._cps2.removeByDomainAndName(browser.currentURI.spec, this.name, ctxt, {
+      handleCompletion: () => {
+        this._isNextContentPrefChangeInternal = true;
+      },
+    });
+  },
+
+  // Utilities
+
+  /**
+   * Returns the zoom change token of the given browser.  Asynchronous
+   * operations that access the given browser's zoom should use this method to
+   * capture the token before starting and use token.isCurrent to determine if
+   * it's safe to access the zoom when done.  If token.isCurrent is false, then
+   * after the async operation started, either the browser's zoom was changed or
+   * the browser was destroyed, and depending on what the operation is doing, it
+   * may no longer be safe to set and get its zoom.
+   *
+   * @param browser  The token of this browser will be returned.
+   * @return  An object with an "isCurrent" getter.
+   */
+  _getBrowserToken: function FullZoom__getBrowserToken(browser) {
+    let map = this._browserTokenMap;
+    if (!map.has(browser)) {
+      map.set(browser, 0);
+    }
+    return {
+      token: map.get(browser),
+      get isCurrent() {
+        // At this point, the browser may have been destructed and unbound but
+        // its outer ID not removed from the map because outer-window-destroyed
+        // hasn't been received yet.  In that case, the browser is unusable, it
+        // has no properties, so return false.  Check for this case by getting a
+        // property, say, docShell.
+        return map.get(browser) === this.token && browser.mInitialized;
+      },
+    };
+  },
+
+  /**
+   * Returns the browser that the supplied zoom event is associated with.
+   * @param event  The zoom event.
+   * @return  The associated browser element, if one exists, otherwise null.
+   */
+  _getTargetedBrowser: function FullZoom__getTargetedBrowser(event) {
+    let target = event.originalTarget;
+
+    // With remote content browsers, the event's target is the browser
+    // we're looking for.
+    const XUL_NS =
+      "http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul";
+    if (
+      window.XULElement.isInstance(target) &&
+      target.localName == "browser" &&
+      target.namespaceURI == XUL_NS
+    ) {
+      return target;
+    }
+
+    // With in-process content browsers, the event's target is the content
+    // document.
+    if (target.nodeType == Node.DOCUMENT_NODE) {
+      return target.ownerGlobal.docShell.chromeEventHandler;
+    }
+
+    throw new Error("Unexpected zoom event source");
+  },
+
+  /**
+   * Increments the zoom change token for the given browser so that pending
+   * async operations know that it may be unsafe to access they zoom when they
+   * finish.
+   *
+   * @param browser  Pending accesses in this browser will be ignored.
+   */
+  _ignorePendingZoomAccesses: function FullZoom__ignorePendingZoomAccesses(
+    browser
+  ) {
+    let map = this._browserTokenMap;
+    map.set(browser, (map.get(browser) || 0) + 1);
+  },
+
+  _ensureValid: function FullZoom__ensureValid(aValue) {
+    // Note that undefined is a valid value for aValue that indicates a known-
+    // not-to-exist value.
+    if (isNaN(aValue)) {
+      return 1;
+    }
+
+    if (aValue < ZoomManager.MIN) {
+      return ZoomManager.MIN;
+    }
+
+    if (aValue > ZoomManager.MAX) {
+      return ZoomManager.MAX;
+    }
+
+    return aValue;
+  },
+
+  // Whether to remember the site specific zoom level for this browser.
+  // This returns false when `browser.zoom.siteSpecific` is false or
+  // the browser has content loaded that should resist fingerprinting.
+  _isSiteSpecific(aBrowser) {
+    if (!this.siteSpecific) {
+      return false;
+    }
+    return !aBrowser?.browsingContext?.topWindowContext
+      .shouldResistFingerprinting;
+  },
+
+  /**
+   * Gets the load context from the given Browser.
+   *
+   * @param Browser  The Browser whose load context will be returned.
+   * @return        The nsILoadContext of the given Browser.
+   */
+  _loadContextFromBrowser: function FullZoom__loadContextFromBrowser(browser) {
+    return browser.loadContext;
+  },
+
+  /**
+   * Asynchronously broadcasts "browser-fullZoom:location-change" so that
+   * listeners can be notified when the zoom levels on those pages change.
+   * The notification is always asynchronous so that observers are guaranteed a
+   * consistent behavior.
+   */
+  _notifyOnLocationChange: function FullZoom__notifyOnLocationChange(browser) {
+    this._executeSoon(function () {
+      Services.obs.notifyObservers(browser, "browser-fullZoom:location-change");
+    });
+  },
+
+  _executeSoon: function FullZoom__executeSoon(callback) {
+    if (!callback) {
+      return;
+    }
+    Services.tm.dispatchToMainThread(callback);
+  },
+
+  _isPDFViewer(browser) {
+    return !!(
+      browser.contentPrincipal.spec == "resource://pdf.js/web/viewer.html"
+    );
+  },
+};