--- a/browser/components/extensions/ext-browser.js
+++ b/browser/components/extensions/ext-browser.js
@@ -512,18 +512,17 @@ class TabTracker extends TabTrackerBase 
       this.emit("tab-removed", {nativeTab, tabId, windowId, isWindowClosing});
     });
   }
 
   getBrowserData(browser) {
     if (browser.ownerDocument.documentURI === "about:addons") {
       // When we're loaded into a <browser> inside about:addons, we need to go up
       // one more level.
-      browser = browser.ownerGlobal.QueryInterface(Ci.nsIInterfaceRequestor)
-                       .getInterface(Ci.nsIDocShell)
+      browser = browser.ownerGlobal.document.docShell
                        .chromeEventHandler;
     }
 
     let result = {
       tabId: -1,
       windowId: -1,
     };
 

--- a/browser/components/extensions/ext-tabs.js
+++ b/browser/components/extensions/ext-tabs.js
@@ -729,19 +729,17 @@ this.tabs = class extends ExtensionAPI {
 
 
           let zoomListener = event => {
             let browser = event.originalTarget;
 
             // For non-remote browsers, this event is dispatched on the document
             // rather than on the <browser>.
             if (browser instanceof Ci.nsIDOMDocument) {
-              browser = browser.defaultView.QueryInterface(Ci.nsIInterfaceRequestor)
-                               .getInterface(Ci.nsIDocShell)
-                               .chromeEventHandler;
+              browser = browser.docShell.chromeEventHandler;
             }
 
             let {gBrowser} = browser.ownerGlobal;
             let nativeTab = gBrowser.getTabForBrowser(browser);
             if (!nativeTab) {
               // We only care about zoom events in the top-level browser of a tab.
               return;
             }

--- a/toolkit/components/extensions/ExtensionCommon.jsm
+++ b/toolkit/components/extensions/ExtensionCommon.jsm
@@ -190,18 +190,17 @@ class BaseContext {
     this.messageManager = null;
     this.docShell = null;
     this.contentWindow = null;
     this.innerWindowID = 0;
   }
 
   setContentWindow(contentWindow) {
     let {document} = contentWindow;
-    let docShell = contentWindow.QueryInterface(Ci.nsIInterfaceRequestor)
-                                .getInterface(Ci.nsIDocShell);
+    let {docShell} = document;
 
     this.innerWindowID = getInnerWindowID(contentWindow);
     this.messageManager = docShell.QueryInterface(Ci.nsIInterfaceRequestor)
                                   .getInterface(Ci.nsIContentFrameMessageManager);
 
     if (this.incognito == null) {
       this.incognito = PrivateBrowsingUtils.isContentWindowPrivate(contentWindow);
     }

--- a/toolkit/components/extensions/ExtensionPageChild.jsm
+++ b/toolkit/components/extensions/ExtensionPageChild.jsm
@@ -358,18 +358,17 @@ ExtensionPageChild = {
     let context = this.extensionContexts.get(windowId);
     if (context) {
       if (context.extension !== extension) {
         throw new Error("A different extension context already exists for this frame");
       }
       throw new Error("An extension context was already initialized for this frame");
     }
 
-    let mm = contentWindow.QueryInterface(Ci.nsIInterfaceRequestor)
-                          .getInterface(Ci.nsIDocShell)
+    let mm = contentWindow.document.docShell
                           .QueryInterface(Ci.nsIInterfaceRequestor)
                           .getInterface(Ci.nsIContentFrameMessageManager);
 
     let {viewType, tabId, devtoolsToolboxInfo} = getFrameData(mm) || {};
 
     let uri = contentWindow.document.documentURIObject;
 
     if (devtoolsToolboxInfo) {

--- a/toolkit/components/extensions/ExtensionParent.jsm
+++ b/toolkit/components/extensions/ExtensionParent.jsm
@@ -479,18 +479,17 @@ class ExtensionPageContextParent extends
     this.extension.views.add(this);
 
     extension.emit("extension-proxy-context-load", this);
   }
 
   // The window that contains this context. This may change due to moving tabs.
   get xulWindow() {
     let win = this.xulBrowser.ownerGlobal;
-    return win.QueryInterface(Ci.nsIInterfaceRequestor).getInterface(Ci.nsIDocShell)
-              .QueryInterface(Ci.nsIDocShellTreeItem).rootTreeItem
+    return win.document.docShell.rootTreeItem
               .QueryInterface(Ci.nsIInterfaceRequestor).getInterface(Ci.nsIDOMWindow);
   }
 
   get currentWindow() {
     if (this.viewType !== "background") {
       return this.xulWindow;
     }
   }

--- a/toolkit/components/extensions/ext-tabs-base.js
+++ b/toolkit/components/extensions/ext-tabs-base.js
@@ -689,19 +689,18 @@ class WindowBase {
   }
 
   /**
    * @property {nsIXULWindow} xulWindow
    *        The nsIXULWindow object for this browser window.
    *        @readonly
    */
   get xulWindow() {
-    return this.window.QueryInterface(Ci.nsIInterfaceRequestor)
-               .getInterface(Ci.nsIDocShell)
-               .treeOwner.QueryInterface(Ci.nsIInterfaceRequestor)
+    return this.window.document.docShell.treeOwner
+               .QueryInterface(Ci.nsIInterfaceRequestor)
                .getInterface(Ci.nsIXULWindow);
   }
 
   /**
    * Returns true if this window is the current window for the given extension
    * context, false otherwise.
    *
    * @param {BaseContext} context