From d182c953512707cbefa47620f34a81e9c3a9e2df Mon Sep 17 00:00:00 2001
From: Kris Maglione <maglione.k@gmail.com>
Date: Tue, 21 Jul 2020 22:19:19 +0000
Subject: [PATCH] Bug 1651519: Part 2 - Also remove
 nsIDOMWindowUtils::outerWindowID. r=nika,geckoview-reviewers,agi

Differential Revision: https://phabricator.services.mozilla.com/D82957
---
 browser/actors/ContextMenuChild.jsm                    |  2 +-
 browser/actors/LightweightThemeChild.jsm               |  2 +-
 browser/base/content/content-refreshblocker.js         |  2 +-
 browser/base/content/tabbrowser.js                     |  2 +-
 .../test/browser/browser_ext_sidebarAction.js          |  2 +-
 ...wser_615394-SSWindowState_events_setBrowserState.js |  2 +-
 .../client/framework/test/browser_target_from_url.js   |  2 +-
 devtools/client/framework/test/browser_two_tabs.js     |  4 ++--
 devtools/client/fronts/root.js                         |  9 +++------
 devtools/server/actors/targets/browsing-context.js     | 10 +++++-----
 dom/base/nsDOMWindowUtils.cpp                          |  9 ---------
 dom/base/test/browser_messagemanager_unload.js         |  2 +-
 dom/base/test/chrome/test_chromeOuterWindowID.xhtml    |  2 +-
 dom/browser-element/BrowserElementChildPreload.js      |  6 ++----
 dom/browser-element/BrowserElementPromptService.jsm    |  2 +-
 dom/interfaces/base/nsIDOMWindowUtils.idl              |  5 -----
 dom/media/PeerConnection.jsm                           |  2 +-
 dom/tests/mochitest/bugs/test_bug534149.html           |  6 ++----
 .../tests/chrome/test_windowProxyDeadWrapper.html      |  2 +-
 .../tests/mochitest/test_nukeContentWindow.html        |  2 +-
 mobile/android/modules/geckoview/GeckoViewTab.jsm      |  4 +---
 .../modules/geckoview/GeckoViewWebExtension.jsm        |  4 ++--
 testing/marionette/listener.js                         |  2 +-
 toolkit/components/extensions/WebNavigationContent.js  | 10 +---------
 toolkit/components/extensions/parent/ext-tabs-base.js  |  2 +-
 toolkit/components/extensions/parent/ext-theme.js      |  6 ++----
 toolkit/content/widgets/editor.js                      |  2 +-
 toolkit/modules/LightweightThemeConsumer.jsm           |  2 +-
 28 files changed, 37 insertions(+), 70 deletions(-)

diff --git a/browser/actors/ContextMenuChild.jsm b/browser/actors/ContextMenuChild.jsm
index ae761bd5116a..2bb991d16ffc 100644
--- a/browser/actors/ContextMenuChild.jsm
+++ b/browser/actors/ContextMenuChild.jsm
@@ -905,7 +905,7 @@ class ContextMenuChild extends JSWindowActorChild {
     );
 
     context.frameOuterWindowID =
-      context.target.ownerGlobal.windowUtils.outerWindowID;
+      context.target.ownerGlobal.docShell.outerWindowID;
 
     context.frameBrowsingContextID =
       context.target.ownerGlobal.browsingContext.id;
diff --git a/browser/actors/LightweightThemeChild.jsm b/browser/actors/LightweightThemeChild.jsm
index 2ffc90bc1277..b98c8eb7955b 100644
--- a/browser/actors/LightweightThemeChild.jsm
+++ b/browser/actors/LightweightThemeChild.jsm
@@ -30,7 +30,7 @@ class LightweightThemeChild extends JSWindowActorChild {
     }
     // We don't have a message manager, so presumable we're running in a sidebar
     // in the parent process.
-    return this.contentWindow.top.windowUtils.outerWindowID;
+    return this.contentWindow.top.docShell.outerWindowID;
   }
 
   /**
diff --git a/browser/base/content/content-refreshblocker.js b/browser/base/content/content-refreshblocker.js
index 007c959af394..5e31f8375633 100644
--- a/browser/base/content/content-refreshblocker.js
+++ b/browser/base/content/content-refreshblocker.js
@@ -144,7 +144,7 @@ var RefreshBlocker = {
    */
   onRefreshAttempted(aWebProgress, aURI, aDelay, aSameURI) {
     let win = aWebProgress.DOMWindow;
-    let outerWindowID = win.windowUtils.outerWindowID;
+    let outerWindowID = win.docShell.outerWindowID;
 
     let data = {
       URI: aURI.spec,
diff --git a/browser/base/content/tabbrowser.js b/browser/base/content/tabbrowser.js
index 0bb0605c238d..e031fdc0fae4 100644
--- a/browser/base/content/tabbrowser.js
+++ b/browser/base/content/tabbrowser.js
@@ -5199,7 +5199,7 @@
         this._uniquePanelIDCounter = 0;
       }
 
-      let outerID = window.windowUtils.outerWindowID;
+      let outerID = window.docShell.outerWindowID;
 
       // We want panel IDs to be globally unique, that's why we include the
       // window ID. We switched to a monotonic counter as Date.now() lead
diff --git a/browser/components/extensions/test/browser/browser_ext_sidebarAction.js b/browser/components/extensions/test/browser/browser_ext_sidebarAction.js
index be9c85a479fd..ae5ad44e12e8 100644
--- a/browser/components/extensions/test/browser/browser_ext_sidebarAction.js
+++ b/browser/components/extensions/test/browser/browser_ext_sidebarAction.js
@@ -166,7 +166,7 @@ add_task(async function sidebar_isOpen() {
   await sendMessage(extension2, "isOpen", { result: false });
 
   info("Test passing a windowId parameter");
-  let windowId = window.windowUtils.outerWindowID;
+  let windowId = window.docShell.outerWindowID;
   let WINDOW_ID_CURRENT = -2;
   await sendMessage(extension1, "isOpen", { arg: { windowId }, result: true });
   await sendMessage(extension2, "isOpen", { arg: { windowId }, result: false });
diff --git a/browser/components/sessionstore/test/browser_615394-SSWindowState_events_setBrowserState.js b/browser/components/sessionstore/test/browser_615394-SSWindowState_events_setBrowserState.js
index 1cd6216bfdc4..24e7b164eaec 100644
--- a/browser/components/sessionstore/test/browser_615394-SSWindowState_events_setBrowserState.js
+++ b/browser/components/sessionstore/test/browser_615394-SSWindowState_events_setBrowserState.js
@@ -66,7 +66,7 @@ const lameMultiWindowState = {
 };
 
 function getOuterWindowID(aWindow) {
-  return aWindow.windowUtils.outerWindowID;
+  return aWindow.docShell.outerWindowID;
 }
 
 function test() {
diff --git a/devtools/client/framework/test/browser_target_from_url.js b/devtools/client/framework/test/browser_target_from_url.js
index 0b831bb934c1..cdca00178bcb 100644
--- a/devtools/client/framework/test/browser_target_from_url.js
+++ b/devtools/client/framework/test/browser_target_from_url.js
@@ -38,7 +38,7 @@ add_task(async function() {
   }
 
   info("Test browser window");
-  let windowId = window.windowUtils.outerWindowID;
+  let windowId = window.docShell.outerWindowID;
   target = await targetFromURL(
     new URL("http://foo?type=window&id=" + windowId)
   );
diff --git a/devtools/client/framework/test/browser_two_tabs.js b/devtools/client/framework/test/browser_two_tabs.js
index 5bc792042468..1ed856cd3d54 100644
--- a/devtools/client/framework/test/browser_two_tabs.js
+++ b/devtools/client/framework/test/browser_two_tabs.js
@@ -47,8 +47,8 @@ async function checkGetTab(client, tab1, tab2, targetFront1, targetFront2) {
   if (tab1.linkedBrowser.frameLoader.remoteTab) {
     filter.tabId = tab1.linkedBrowser.frameLoader.remoteTab.tabId;
   } else {
-    const windowUtils = tab1.linkedBrowser.contentWindow.windowUtils;
-    filter.outerWindowID = windowUtils.outerWindowID;
+    const { docShell } = tab1.linkedBrowser.contentWindow;
+    filter.outerWindowID = docShell.outerWindowID;
   }
   front = await getTabTarget(client, filter);
   is(
diff --git a/devtools/client/fronts/root.js b/devtools/client/fronts/root.js
index f565375d65f8..6af711b8ba43 100644
--- a/devtools/client/fronts/root.js
+++ b/devtools/client/fronts/root.js
@@ -222,13 +222,10 @@ class RootFront extends FrontClassWithSpec(rootSpec) {
         if (browser.frameLoader.remoteTab) {
           // Tabs in child process
           packet.tabId = browser.frameLoader.remoteTab.tabId;
-        } else if (browser.outerWindowID) {
-          // <xul:browser> tabs in parent process
-          packet.outerWindowID = browser.outerWindowID;
         } else {
-          // <iframe mozbrowser> tabs in parent process
-          const windowUtils = browser.contentWindow.windowUtils;
-          packet.outerWindowID = windowUtils.outerWindowID;
+          // <xul:browser> or <iframe mozbrowser> tabs in parent process
+          packet.outerWindowID =
+            browser.browsingContext.currentWindowGlobal.outerWindowId;
         }
       } else {
         // Throw if a filter object have been passed but without
diff --git a/devtools/server/actors/targets/browsing-context.js b/devtools/server/actors/targets/browsing-context.js
index 5df0b17110d2..8fb8105a544f 100644
--- a/devtools/server/actors/targets/browsing-context.js
+++ b/devtools/server/actors/targets/browsing-context.js
@@ -430,8 +430,8 @@ const browsingContextTargetPrototype = {
   },
 
   get outerWindowID() {
-    if (this.window) {
-      return this.window.windowUtils.outerWindowID;
+    if (this.docShell) {
+      return this.docShell.outerWindowID;
     }
     return null;
   },
@@ -893,7 +893,7 @@ const browsingContextTargetPrototype = {
       .QueryInterface(Ci.nsIInterfaceRequestor)
       .getInterface(Ci.nsIWebProgress);
     const window = webProgress.DOMWindow;
-    const id = window.windowUtils.outerWindowID;
+    const id = docShell.outerWindowID;
     let parentID = undefined;
     // Ignore the parent of the original document on non-e10s firefox,
     // as we get the xul window as parent and don't care about it.
@@ -905,7 +905,7 @@ const browsingContextTargetPrototype = {
       window.parent != window &&
       window != this._originalWindow
     ) {
-      parentID = window.parent.windowUtils.outerWindowID;
+      parentID = window.parent.docShell.outerWindowID;
     }
 
     return {
@@ -952,7 +952,7 @@ const browsingContextTargetPrototype = {
     }
 
     webProgress = webProgress.QueryInterface(Ci.nsIWebProgress);
-    const id = webProgress.DOMWindow.windowUtils.outerWindowID;
+    const id = webProgress.DOMWindow.docShell.outerWindowID;
     this.emit("frameUpdate", {
       frames: [
         {
diff --git a/dom/base/nsDOMWindowUtils.cpp b/dom/base/nsDOMWindowUtils.cpp
index a1a12f539806..f514dcdbd408 100644
--- a/dom/base/nsDOMWindowUtils.cpp
+++ b/dom/base/nsDOMWindowUtils.cpp
@@ -2137,15 +2137,6 @@ nsDOMWindowUtils::SetDesktopModeViewport(bool aDesktopMode) {
   return NS_OK;
 }
 
-NS_IMETHODIMP
-nsDOMWindowUtils::GetOuterWindowID(uint64_t* aWindowID) {
-  nsCOMPtr<nsPIDOMWindowOuter> window = do_QueryReferent(mWindow);
-  NS_ENSURE_STATE(window);
-
-  *aWindowID = window->WindowID();
-  return NS_OK;
-}
-
 NS_IMETHODIMP
 nsDOMWindowUtils::SuspendTimeouts() {
   nsCOMPtr<nsPIDOMWindowOuter> window = do_QueryReferent(mWindow);
diff --git a/dom/base/test/browser_messagemanager_unload.js b/dom/base/test/browser_messagemanager_unload.js
index 9cd86ed09e35..d4d42a94477c 100644
--- a/dom/base/test/browser_messagemanager_unload.js
+++ b/dom/base/test/browser_messagemanager_unload.js
@@ -15,7 +15,7 @@ function frameScript() {
     ]);
   }
 
-  let outerID = content.windowUtils.outerWindowID;
+  let outerID = content.docShell.outerWindowID;
   function onOuterWindowDestroyed(subject, topic, data) {
     if (docShell) {
       sendAsyncMessage("Test:Fail", "docShell is non-null");
diff --git a/dom/base/test/chrome/test_chromeOuterWindowID.xhtml b/dom/base/test/chrome/test_chromeOuterWindowID.xhtml
index 13eba45152c3..cca49158174e 100644
--- a/dom/base/test/chrome/test_chromeOuterWindowID.xhtml
+++ b/dom/base/test/chrome/test_chromeOuterWindowID.xhtml
@@ -28,7 +28,7 @@ windows.
   const TEST_PAGE_2 = "http://example.com/browser";
 
   function getOuterWindowID(win) {
-    return win.windowUtils.outerWindowID;
+    return win.docShell.outerWindowID;
   }
 
   /**
diff --git a/dom/browser-element/BrowserElementChildPreload.js b/dom/browser-element/BrowserElementChildPreload.js
index 8cf7bb1b5ba0..f760518ca86c 100644
--- a/dom/browser-element/BrowserElementChildPreload.js
+++ b/dom/browser-element/BrowserElementChildPreload.js
@@ -145,10 +145,8 @@ BrowserElementChild.prototype = {
    * Show a modal prompt.  Called by BrowserElementPromptService.
    */
   showModalPrompt(win, args) {
-    let utils = win.windowUtils;
-
     args.windowID = {
-      outer: utils.outerWindowID,
+      outer: win.docShell.outerWindowID,
       inner: this._tryGetInnerWindowID(win),
     };
     sendAsyncMsg("showmodalprompt", args);
@@ -173,7 +171,7 @@ BrowserElementChild.prototype = {
     debug("_waitForResult(" + win + ")");
     let utils = win.windowUtils;
 
-    let outerWindowID = utils.outerWindowID;
+    let outerWindowID = win.docShell.outerWindowID;
     let innerWindowID = this._tryGetInnerWindowID(win);
     if (innerWindowID === null) {
       // I have no idea what waiting for a result means when there's no inner
diff --git a/dom/browser-element/BrowserElementPromptService.jsm b/dom/browser-element/BrowserElementPromptService.jsm
index c40753d2d6fa..12189efd4374 100644
--- a/dom/browser-element/BrowserElementPromptService.jsm
+++ b/dom/browser-element/BrowserElementPromptService.jsm
@@ -687,7 +687,7 @@ var BrowserElementPromptService = {
   },
 
   _getOuterWindowID(win) {
-    return win.windowUtils.outerWindowID;
+    return win.docShell.outerWindowID;
   },
 
   _browserElementChildMap: {},
diff --git a/dom/interfaces/base/nsIDOMWindowUtils.idl b/dom/interfaces/base/nsIDOMWindowUtils.idl
index b34a954032c3..075ae52693c9 100644
--- a/dom/interfaces/base/nsIDOMWindowUtils.idl
+++ b/dom/interfaces/base/nsIDOMWindowUtils.idl
@@ -1293,11 +1293,6 @@ interface nsIDOMWindowUtils : nsISupports {
                                            in AString aPseudoElement,
                                            in AString aPropertyName);
 
-  /**
-   * Get the id of the outer window of this window.  This will never throw.
-   */
-  readonly attribute unsigned long long outerWindowID;
-
   /**
    * Put the window into a state where scripts are frozen and events
    * suppressed, for use when the window has launched a modal prompt.
diff --git a/dom/media/PeerConnection.jsm b/dom/media/PeerConnection.jsm
index 5d02f70e27a9..9183176c0edd 100644
--- a/dom/media/PeerConnection.jsm
+++ b/dom/media/PeerConnection.jsm
@@ -1021,7 +1021,7 @@ class RTCPeerConnection {
       } else {
         this._havePermission = new Promise((resolve, reject) => {
           this._settlePermission = { allow: resolve, deny: reject };
-          let outerId = this._win.windowUtils.outerWindowID;
+          let outerId = this._win.docShell.outerWindowID;
 
           let chrome = new CreateOfferRequest(
             outerId,
diff --git a/dom/tests/mochitest/bugs/test_bug534149.html b/dom/tests/mochitest/bugs/test_bug534149.html
index 2d8180e79901..8c1a8b7e4d65 100644
--- a/dom/tests/mochitest/bugs/test_bug534149.html
+++ b/dom/tests/mochitest/bugs/test_bug534149.html
@@ -23,10 +23,8 @@ function getIDs(iframe) {
   // Force inner creation
   win.document;
 
-  return [
-    SpecialPowers.getDOMWindowUtils(win).outerWindowID,
-    SpecialPowers.wrap(win).windowGlobalChild.innerWindowId,
-  ];
+  let wgc = SpecialPowers.wrap(win).windowGlobalChild;
+  return [wgc.outerWindowId, wgc.innerWindowId];
 }
 
 var i1 = document.createElement("iframe");
diff --git a/js/xpconnect/tests/chrome/test_windowProxyDeadWrapper.html b/js/xpconnect/tests/chrome/test_windowProxyDeadWrapper.html
index adb4059e7790..9d8a2a77618d 100644
--- a/js/xpconnect/tests/chrome/test_windowProxyDeadWrapper.html
+++ b/js/xpconnect/tests/chrome/test_windowProxyDeadWrapper.html
@@ -43,7 +43,7 @@ async function go() {
             return;
         }
 
-        let winID = w.windowUtils.outerWindowID;
+        let winID = w.docShell.outerWindowID;
         // Remove the frame. This will nuke the WindowProxy wrapper from our chrome
         // document's global, so evaluating 'this' in it will return a dead wrapper
         // once the window is destroyed.
diff --git a/js/xpconnect/tests/mochitest/test_nukeContentWindow.html b/js/xpconnect/tests/mochitest/test_nukeContentWindow.html
index 2d9299f4b935..0db8749b5928 100644
--- a/js/xpconnect/tests/mochitest/test_nukeContentWindow.html
+++ b/js/xpconnect/tests/mochitest/test_nukeContentWindow.html
@@ -37,7 +37,7 @@ add_task(async function() {
   await new Promise(resolve => frame.addEventListener("load", resolve, {once: true}));
 
   let win = frame.contentWindow;
-  let winID = SpecialPowers.getDOMWindowUtils(win).outerWindowID;
+  let winID = SpecialPowers.wrap(win).docShell.outerWindowID;
 
   win.eval("obj = {}");
   win.obj.foo = {bar: "baz"};
diff --git a/mobile/android/modules/geckoview/GeckoViewTab.jsm b/mobile/android/modules/geckoview/GeckoViewTab.jsm
index 87e40ef499b4..4a2fccb24355 100644
--- a/mobile/android/modules/geckoview/GeckoViewTab.jsm
+++ b/mobile/android/modules/geckoview/GeckoViewTab.jsm
@@ -21,9 +21,7 @@ XPCOMUtils.defineLazyModuleGetters(this, {
 
 class Tab {
   constructor(window) {
-    this.id = GeckoViewTabBridge.windowIdToTabId(
-      window.windowUtils.outerWindowID
-    );
+    this.id = GeckoViewTabBridge.windowIdToTabId(window.docShell.outerWindowID);
     this.browser = window.browser;
     this.active = false;
   }
diff --git a/mobile/android/modules/geckoview/GeckoViewWebExtension.jsm b/mobile/android/modules/geckoview/GeckoViewWebExtension.jsm
index 5794a293cf0e..33db765645a8 100644
--- a/mobile/android/modules/geckoview/GeckoViewWebExtension.jsm
+++ b/mobile/android/modules/geckoview/GeckoViewWebExtension.jsm
@@ -518,7 +518,7 @@ class MobileWindowTracker extends EventEmitter {
   }
 
   setTabActive(aWindow, aActive) {
-    const { browser, tab, windowUtils } = aWindow;
+    const { browser, tab, docShell } = aWindow;
     tab.active = aActive;
 
     if (aActive) {
@@ -528,7 +528,7 @@ class MobileWindowTracker extends EventEmitter {
         this._topNonPBWindow = this._topWindow;
       }
       this.emit("tab-activated", {
-        windowId: windowUtils.outerWindowID,
+        windowId: docShell.outerWindowID,
         tabId: tab.id,
         isPrivate,
       });
diff --git a/testing/marionette/listener.js b/testing/marionette/listener.js
index a6036ad53ab2..b00962141ce4 100644
--- a/testing/marionette/listener.js
+++ b/testing/marionette/listener.js
@@ -385,7 +385,7 @@ const loadListener = {
       // In the case when the currently selected frame is closed,
       // there will be no further load events. Stop listening immediately.
       case "outer-window-destroyed":
-        if (bc.window.windowUtils.outerWindowID == winId) {
+        if (bc.currentWindowContext.outerWindowId == winId) {
           this.stop();
           sendOk(this.commandID);
         }
diff --git a/toolkit/components/extensions/WebNavigationContent.js b/toolkit/components/extensions/WebNavigationContent.js
index 7ed5f0d1b0a5..08ada223d691 100644
--- a/toolkit/components/extensions/WebNavigationContent.js
+++ b/toolkit/components/extensions/WebNavigationContent.js
@@ -14,14 +14,6 @@ ChromeUtils.defineModuleGetter(
   "resource://gre/modules/WebNavigationFrames.jsm"
 );
 
-function getDocShellOuterWindowId(docShell) {
-  if (!docShell) {
-    return undefined;
-  }
-
-  return docShell.domWindow.windowUtils.outerWindowID;
-}
-
 function loadListener(event) {
   let document = event.target;
   let window = document.defaultView;
@@ -95,7 +87,7 @@ var CreatedNavigationTargetListener = {
     const sourceFrameId = WebNavigationFrames.getFrameId(
       sourceDocShell.browsingContext
     );
-    const createdOuterWindowId = getDocShellOuterWindowId(sourceDocShell);
+    const createdOuterWindowId = sourceDocShell?.outerWindowID;
 
     let url;
     if (props.hasKey("url")) {
diff --git a/toolkit/components/extensions/parent/ext-tabs-base.js b/toolkit/components/extensions/parent/ext-tabs-base.js
index 61ee7a6e0115..9011cae3e71d 100644
--- a/toolkit/components/extensions/parent/ext-tabs-base.js
+++ b/toolkit/components/extensions/parent/ext-tabs-base.js
@@ -1455,7 +1455,7 @@ class WindowTrackerBase extends EventEmitter {
     });
 
     this._windowIds = new DefaultWeakMap(window => {
-      return window.windowUtils.outerWindowID;
+      return window.docShell.outerWindowID;
     });
   }
 
diff --git a/toolkit/components/extensions/parent/ext-theme.js b/toolkit/components/extensions/parent/ext-theme.js
index cb8d418ef983..84433910daf6 100644
--- a/toolkit/components/extensions/parent/ext-theme.js
+++ b/toolkit/components/extensions/parent/ext-theme.js
@@ -118,7 +118,7 @@ class Theme {
     if (this.windowId) {
       this.lwtData.window = windowTracker.getWindow(
         this.windowId
-      ).windowUtils.outerWindowID;
+      ).docShell.outerWindowID;
       windowOverrides.set(this.windowId, this);
     } else {
       windowOverrides.clear();
@@ -384,9 +384,7 @@ class Theme {
     };
 
     if (windowId) {
-      lwtData.window = windowTracker.getWindow(
-        windowId
-      ).windowUtils.outerWindowID;
+      lwtData.window = windowTracker.getWindow(windowId).docShell.outerWindowID;
       windowOverrides.delete(windowId);
     } else {
       windowOverrides.clear();
diff --git a/toolkit/content/widgets/editor.js b/toolkit/content/widgets/editor.js
index a8bdf61e9691..1edd6cb088ad 100644
--- a/toolkit/content/widgets/editor.js
+++ b/toolkit/content/widgets/editor.js
@@ -172,7 +172,7 @@
     }
 
     get outerWindowID() {
-      return this.contentWindow.windowUtils.outerWindowID;
+      return this.docShell.outerWindowID;
     }
 
     makeEditable(editortype, waitForUrlLoad) {
diff --git a/toolkit/modules/LightweightThemeConsumer.jsm b/toolkit/modules/LightweightThemeConsumer.jsm
index 198d9a73312c..133ce377a05b 100644
--- a/toolkit/modules/LightweightThemeConsumer.jsm
+++ b/toolkit/modules/LightweightThemeConsumer.jsm
@@ -207,7 +207,7 @@ const toolkitVariableMap = [
 function LightweightThemeConsumer(aDocument) {
   this._doc = aDocument;
   this._win = aDocument.defaultView;
-  this._winId = this._win.windowUtils.outerWindowID;
+  this._winId = this._win.docShell.outerWindowID;
 
   Services.obs.addObserver(this, "lightweight-theme-styling-update");