--- a/browser/components/extensions/ext-tabs.js
+++ b/browser/components/extensions/ext-tabs.js
@@ -71,17 +71,20 @@ extensions.on("page-shutdown", (type, co
       if (tab) {
         gBrowser.removeTab(tab);
       }
     }
   }
 });
 
 extensions.on("fill-browser-data", (type, browser, data) => {
-  data.tabId = browser ? TabManager.getBrowserId(browser) : -1;
+  let gBrowser = browser && browser.ownerGlobal.gBrowser;
+  let tab = gBrowser && gBrowser.getTabForBrowser(browser);
+  data.tabId = tab ? TabManager.getId(tab) : -1;
+  data.windowId = tab ? WindowManager.getId(tab.ownerGlobal) : -1;
 });
 /* eslint-enable mozilla/balanced-listeners */
 
 global.currentWindow = function(context) {
   let {xulWindow} = context;
   if (xulWindow && context.viewType != "background") {
     return xulWindow;
   }
@@ -135,17 +138,17 @@ let tabListener = {
         } else {
           this.emitRemoved(tab, false);
         }
         break;
     }
   },
 
   handleWindowOpen(window) {
-    if (window.arguments[0] instanceof window.XULElement) {
+    if (window.arguments && window.arguments[0] instanceof window.XULElement) {
       // If the first window argument is a XUL element, it means the
       // window is about to adopt a tab from another window to replace its
       // initial tab.
       //
       // Note that this event handler depends on running before the
       // delayed startup code in browser.js, which is currently triggered
       // by the first MozAfterPaint event. That code handles finally
       // adopting the tab, and clears it from the arguments list in the

--- a/toolkit/components/extensions/ext-webRequest.js
+++ b/toolkit/components/extensions/ext-webRequest.js
@@ -22,39 +22,46 @@ function WebRequestEventManager(context,
   let name = `webRequest.${eventName}`;
   let register = (callback, filter, info) => {
     let listener = data => {
       // Prevent listening in on requests originating from system principal to
       // prevent tinkering with OCSP, app and addon updates, etc.
       if (data.isSystemPrincipal) {
         return;
       }
+      let browserData = {};
+      extensions.emit("fill-browser-data", data.browser, browserData);
+      if (filter.tabId != null && browserData.tabId != filter.tabId) {
+        return;
+      }
+      if (filter.windowId != null && browserData.windowId != filter.windowId) {
+        return;
+      }
 
       let data2 = {
         requestId: data.requestId,
         url: data.url,
         originUrl: data.originUrl,
         method: data.method,
+        tabId: browserData.tabId,
         type: data.type,
         timeStamp: Date.now(),
         frameId: ExtensionManagement.getFrameId(data.windowId),
         parentFrameId: ExtensionManagement.getParentFrameId(data.parentWindowId, data.windowId),
       };
 
       const maybeCached = ["onResponseStarted", "onBeforeRedirect", "onCompleted", "onErrorOccurred"];
       if (maybeCached.includes(eventName)) {
         data2.fromCache = !!data.fromCache;
       }
 
       if ("ip" in data) {
         data2.ip = data.ip;
       }
 
-      extensions.emit("fill-browser-data", data.browser, data2);
-
       let optional = ["requestHeaders", "responseHeaders", "statusCode", "statusLine", "error", "redirectUrl",
                       "requestBody"];
       for (let opt of optional) {
         if (opt in data) {
           data2[opt] = data[opt];
         }
       }
 

--- a/toolkit/components/extensions/test/mochitest/head_webrequest.js
+++ b/toolkit/components/extensions/test/mochitest/head_webrequest.js
@@ -154,36 +154,33 @@ function background(events) {
       let expected = getExpected(details);
       if (!expected) {
         return result;
       }
       let expectedEvent = expected.events[0] == name;
       if (expectedEvent) {
         expected.events.shift();
       } else {
-        expectedEvent = expected.optional_events[0] == name;
-        if (expectedEvent) {
-          expected.optional_events.shift();
-        }
+        // e10s vs. non-e10s errors can end with either onCompleted or onErrorOccurred
+        expectedEvent = expected.optional_events.includes(name);
       }
       browser.test.assertTrue(expectedEvent, `received ${name}`);
       browser.test.assertEq(expected.type, details.type, "resource type is correct");
       browser.test.assertEq(expected.origin || defaultOrigin, details.originUrl, "origin is correct");
 
       if (name == "onBeforeRequest") {
         // Save some values to test request consistency in later events.
         browser.test.assertTrue(details.tabId !== undefined, `tabId ${details.tabId}`);
         browser.test.assertTrue(details.requestId !== undefined, `requestId ${details.requestId}`);
         // Validate requestId if it's already set, this happens with redirects.
         if (expected.test.requestId !== undefined) {
           browser.test.assertEq("string", typeof expected.test.requestId, `requestid ${expected.test.requestId} is string`);
           browser.test.assertEq("string", typeof details.requestId, `requestid ${details.requestId} is string`);
           browser.test.assertEq("number", typeof parseInt(details.requestId, 10), "parsed requestid is number");
-          browser.test.assertNotEq(expected.test.requestId, details.requestId,
-                                  `last requestId ${expected.test.requestId} different from this one ${details.requestId}`);
+          browser.test.assertEq(expected.test.requestId, details.requestId, "redirects will keep the same requestId");
         } else {
           // Save any values we want to validate in later events.
           expected.test.requestId = details.requestId;
           expected.test.tabId = details.tabId;
         }
         // Tests we don't need to do every event.
         browser.test.assertTrue(details.type.toUpperCase() in browser.webRequest.ResourceType, `valid resource type ${details.type}`);
       } else {

--- a/toolkit/components/extensions/test/mochitest/mochitest.ini
+++ b/toolkit/components/extensions/test/mochitest/mochitest.ini
@@ -91,16 +91,18 @@ skip-if = (os == 'android') # Android do
 [test_ext_i18n.html]
 skip-if = (os == 'android') # Bug 1258975 on android.
 [test_ext_web_accessible_resources.html]
 skip-if = (os == 'android') # Bug 1258975 on android.
 [test_ext_webrequest_background_events.html]
 skip-if = os == 'android' # webrequest api unsupported (bug 1258975).
 [test_ext_webrequest_basic.html]
 skip-if = os == 'android' # webrequest api unsupported (bug 1258975).
+[test_ext_webrequest_filter.html]
+skip-if = os == 'android' # webrequest api unsupported (bug 1258975).
 [test_ext_webrequest_suspend.html]
 skip-if = os == 'android' # webrequest api unsupported (bug 1258975).
 [test_ext_webrequest_upload.html]
 skip-if = os == 'android' # webrequest api unsupported (bug 1258975).
 [test_ext_webnavigation.html]
 skip-if = os == 'android' # port.sender.tab is undefined on Android (bug 1258975).
 [test_ext_webnavigation_filters.html]
 skip-if = os == 'android' # port.sender.tab is undefined on Android (bug 1258975).

new file mode 100644
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_webrequest_filter.html
@@ -0,0 +1,181 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+<meta charset="utf-8">
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/SpawnTask.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <script type="text/javascript" src="head_webrequest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+<script>
+"use strict";
+
+let windowData, testWindow;
+
+add_task(function* setup() {
+  testWindow = window.open("about:blank", "_blank", "width=100,height=100");
+  yield waitForLoad(testWindow);
+
+  // Fetch the windowId and tabId we need to filter with WebRequest.
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: [
+        "tabs",
+      ],
+    },
+    background() {
+      browser.windows.getCurrent({populate: true}).then(window => {
+        browser.test.log(`current window ${window.id} tabs: ${JSON.stringify(window.tabs.map(tab => [tab.id, tab.url]))}`);
+        browser.test.sendMessage("windowData", {windowId: window.id, tabId: window.tabs[0].id});
+      });
+    },
+  });
+  yield extension.startup();
+  windowData = yield extension.awaitMessage("windowData");
+  info(`window is ${JSON.stringify(windowData)}`);
+  yield extension.unload();
+});
+
+add_task(function* test_webRequest_filter_window() {
+  yield SpecialPowers.pushPrefEnv({
+    set: [["dom.serviceWorkers.testing.enabled", true]],
+  });
+
+  let events = {
+    "onBeforeRequest":     [{urls: ["<all_urls>"], windowId: windowData.windowId}],
+    "onBeforeSendHeaders": [{urls: ["<all_urls>"], windowId: windowData.windowId}, ["requestHeaders"]],
+    "onSendHeaders":       [{urls: ["<all_urls>"], windowId: windowData.windowId}, ["requestHeaders"]],
+    "onBeforeRedirect":    [{urls: ["<all_urls>"], windowId: windowData.windowId}],
+    "onHeadersReceived":   [{urls: ["<all_urls>"], windowId: windowData.windowId}, ["responseHeaders"]],
+    "onResponseStarted":   [{urls: ["<all_urls>"], windowId: windowData.windowId}],
+    "onCompleted":         [{urls: ["<all_urls>"], windowId: windowData.windowId}, ["responseHeaders"]],
+    "onErrorOccurred":     [{urls: ["<all_urls>"], windowId: windowData.windowId}],
+  };
+  let expect = {
+    "file_image_bad.png": {
+      optional_events: ["onBeforeRedirect", "onBeforeRequest", "onBeforeSendHeaders", "onSendHeaders"],
+      type: "main_frame",
+    },
+  };
+
+  let extension = makeExtension(events);
+  yield extension.startup();
+  extension.sendMessage("set-expected", {expect, origin: location.href});
+  yield extension.awaitMessage("continue");
+
+  // We should not get events for a new window load.
+  let newWindow = window.open("file_image_good.png", "_blank", "width=100,height=100");
+  yield waitForLoad(newWindow);
+  newWindow.close();
+
+  // We should not get background events.
+  let registration = yield navigator.serviceWorker.register("webrequest_worker.js?test0", {scope: "."});
+
+  // We should get events for the reload.
+  testWindow.location = "file_image_bad.png";
+  yield extension.awaitMessage("done");
+
+  yield registration.unregister();
+  yield extension.unload();
+});
+
+add_task(function* test_webRequest_filter_tab() {
+  yield SpecialPowers.pushPrefEnv({
+    set: [["dom.serviceWorkers.testing.enabled", true]],
+  });
+
+  let events = {
+    "onBeforeRequest":     [{urls: ["<all_urls>"], tabId: windowData.tabId}],
+    "onBeforeSendHeaders": [{urls: ["<all_urls>"], tabId: windowData.tabId}, ["requestHeaders"]],
+    "onSendHeaders":       [{urls: ["<all_urls>"], tabId: windowData.tabId}, ["requestHeaders"]],
+    "onBeforeRedirect":    [{urls: ["<all_urls>"], tabId: windowData.tabId}],
+    "onHeadersReceived":   [{urls: ["<all_urls>"], tabId: windowData.tabId}, ["responseHeaders"]],
+    "onResponseStarted":   [{urls: ["<all_urls>"], tabId: windowData.tabId}],
+    "onCompleted":         [{urls: ["<all_urls>"], tabId: windowData.tabId}, ["responseHeaders"]],
+    "onErrorOccurred":     [{urls: ["<all_urls>"], tabId: windowData.tabId}],
+  };
+  let expect = {
+    "file_image_good.png": {
+      optional_events: ["onBeforeRedirect", "onBeforeRequest", "onBeforeSendHeaders", "onSendHeaders"],
+      type: "main_frame",
+      cached: true,
+    },
+  };
+
+  let extension = makeExtension(events);
+  yield extension.startup();
+  extension.sendMessage("set-expected", {expect, origin: location.href});
+  yield extension.awaitMessage("continue");
+
+  // We should not get events for a new window load.
+  let newWindow = window.open("file_image_good.png", "_blank", "width=100,height=100");
+  yield waitForLoad(newWindow);
+  newWindow.close();
+
+  // We should not get background events.
+  let registration = yield navigator.serviceWorker.register("webrequest_worker.js?test1", {scope: "."});
+
+  // We should get events for the reload.
+  testWindow.location = "file_image_good.png";
+  yield extension.awaitMessage("done");
+
+  yield registration.unregister();
+  yield extension.unload();
+});
+
+
+add_task(function* test_webRequest_filter_background() {
+  yield SpecialPowers.pushPrefEnv({
+    set: [["dom.serviceWorkers.testing.enabled", true]],
+  });
+
+  let events = {
+    "onBeforeRequest":     [{urls: ["<all_urls>"], tabId: -1}],
+    "onBeforeSendHeaders": [{urls: ["<all_urls>"], tabId: -1}, ["requestHeaders"]],
+    "onSendHeaders":       [{urls: ["<all_urls>"], tabId: -1}, ["requestHeaders"]],
+    "onBeforeRedirect":    [{urls: ["<all_urls>"], tabId: -1}],
+    "onHeadersReceived":   [{urls: ["<all_urls>"], tabId: -1}, ["responseHeaders"]],
+    "onResponseStarted":   [{urls: ["<all_urls>"], tabId: -1}],
+    "onCompleted":         [{urls: ["<all_urls>"], tabId: -1}, ["responseHeaders"]],
+    "onErrorOccurred":     [{urls: ["<all_urls>"], tabId: -1}],
+  };
+  let expect = {
+    "webrequest_worker.js": {
+      type: "script",
+    },
+    "example.txt": {
+      status: 404,
+      events: ["onBeforeRequest", "onBeforeSendHeaders", "onSendHeaders", "onHeadersReceived", "onResponseStarted"],
+      optional_events: ["onCompleted", "onErrorOccurred"],
+      type: "other",
+      origin: SimpleTest.getTestFileURL("webrequest_worker.js?test2"),
+    },
+  };
+
+  let extension = makeExtension(events);
+  yield extension.startup();
+  extension.sendMessage("set-expected", {expect, origin: location.href});
+  yield extension.awaitMessage("continue");
+
+  // We should not get events for a window.
+  testWindow.location = "file_image_bad.png";
+
+  // We should get events for the background page.
+  let registration = yield navigator.serviceWorker.register(SimpleTest.getTestFileURL("webrequest_worker.js?test2"), {scope: "."});
+  yield extension.awaitMessage("done");
+  yield registration.unregister();
+
+  yield extension.unload();
+});
+
+add_task(function* teardown() {
+  testWindow.close();
+});
+</script>
+</head>
+<body>
+
+</body>
+</html>