diff --git a/toolkit/components/extensions/ext-webRequest.js b/toolkit/components/extensions/ext-webRequest.js
index 793d08a2c897..6796d9c54cef 100644
--- a/toolkit/components/extensions/ext-webRequest.js
+++ b/toolkit/components/extensions/ext-webRequest.js
@@ -33,6 +33,7 @@ function WebRequestEventManager(context, eventName) {
       }
 
       let data2 = {
+        requestId: data.requestId,
         url: data.url,
         method: data.method,
         type: data.type,
diff --git a/toolkit/components/extensions/test/mochitest/file_WebRequest_page1.html b/toolkit/components/extensions/test/mochitest/file_WebRequest_page1.html
index 218ccc5d22e3..6308d424aa1b 100644
--- a/toolkit/components/extensions/test/mochitest/file_WebRequest_page1.html
+++ b/toolkit/components/extensions/test/mochitest/file_WebRequest_page1.html
@@ -25,5 +25,7 @@
 
 <iframe src="file_WebRequest_page2.html" width="200" height="200"></iframe>
 <iframe src="redirection.sjs" width="200" height="200"></iframe>
+<iframe src="data:text/plain,webRequestTest" width="200" height="200"></iframe>
+
 </body>
 </html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_webrequest.html b/toolkit/components/extensions/test/mochitest/test_ext_webrequest.html
index 2c578a5592e9..056cda91f774 100644
--- a/toolkit/components/extensions/test/mochitest/test_ext_webrequest.html
+++ b/toolkit/components/extensions/test/mochitest/test_ext_webrequest.html
@@ -31,7 +31,9 @@ const expected_requested = [BASE + "/file_WebRequest_page1.html",
                             BASE + "/file_WebRequest_page2.html",
                             BASE + "/nonexistent_script_url.js",
                             BASE + "/redirection.sjs",
-                            BASE + "/xhr_resource"];
+                            BASE + "/dummy_page.html",
+                            BASE + "/xhr_resource",
+                            "data:text/plain,webRequestTest"];
 
 const expected_beforeSendHeaders = [BASE + "/file_WebRequest_page1.html",
                               BASE + "/file_style_good.css",
@@ -53,7 +55,7 @@ const expected_sendHeaders = expected_beforeSendHeaders.filter(u => !/_redirect\
 const expected_redirect = expected_beforeSendHeaders.filter(u => /_redirect\./.test(u))
                             .concat(BASE + "/redirection.sjs");
 
-const expected_complete = [BASE + "/file_WebRequest_page1.html",
+const expected_response = [BASE + "/file_WebRequest_page1.html",
                            BASE + "/file_style_good.css",
                            BASE + "/file_image_good.png",
                            BASE + "/file_script_good.js",
@@ -63,6 +65,8 @@ const expected_complete = [BASE + "/file_WebRequest_page1.html",
                            BASE + "/dummy_page.html",
                            BASE + "/xhr_resource"];
 
+const expected_complete = expected_response.concat("data:text/plain,webRequestTest");
+
 function removeDupes(list) {
   let j = 0;
   for (let i = 1; i < list.length; i++) {
@@ -85,11 +89,13 @@ function compareLists(list1, list2, kind) {
 }
 
 function backgroundScript() {
-  const BASE = "http://mochi.test:8888/tests/toolkit/components/extensions/test/mochitest";
-
   let checkCompleted = true;
   let savedTabId = -1;
 
+  function shouldRecord(url) {
+    return url.startsWith(BASE) || /^data:.*\bwebRequestTest\b/.test(url);
+  }
+
   function checkType(details) {
     let expected_type = "???";
     if (details.url.indexOf("style") != -1) {
@@ -100,7 +106,7 @@ function backgroundScript() {
       expected_type = "script";
     } else if (details.url.indexOf("page1") != -1) {
       expected_type = "main_frame";
-    } else if (/page2|redirection|dummy_page/.test(details.url)) {
+    } else if (/page2|redirection|dummy_page|data:text\/(?:plain|html),/.test(details.url)) {
       expected_type = "sub_frame";
     } else if (details.url.indexOf("xhr") != -1) {
       expected_type = "xmlhttprequest";
@@ -108,6 +114,11 @@ function backgroundScript() {
     browser.test.assertEq(details.type, expected_type, "resource type is correct");
   }
 
+  let requestIDs = new Map();
+  function checkRequestId(details) {
+    browser.test.assertEq(requestIDs.get(details.url), details.requestId, `correct requestId for ${details.url} (${details.requestId})`);
+  }
+
   let frameIDs = new Map();
 
   let recorded = {requested: [],
@@ -123,9 +134,13 @@ function backgroundScript() {
   }
 
   function onBeforeRequest(details) {
-    browser.test.log(`onBeforeRequest ${details.url}`);
+    browser.test.log(`onBeforeRequest ${details.requestId} ${details.url}`);
+
+    browser.test.assertTrue(details.requestId > 0, `valid request ID ${details.requestId}`);
+    requestIDs.set(details.url, details.requestId);
+
     checkResourceType(details.type);
-    if (details.url.startsWith(BASE)) {
+    if (shouldRecord(details.url)) {
       recorded.requested.push(details.url);
 
       if (savedTabId == -1) {
@@ -155,8 +170,9 @@ function backgroundScript() {
 
   function onBeforeSendHeaders(details) {
     browser.test.log(`onBeforeSendHeaders ${details.url}`);
+    checkRequestId(details);
     checkResourceType(details.type);
-    if (details.url.startsWith(BASE)) {
+    if (shouldRecord(details.url)) {
       recorded.beforeSendHeaders.push(details.url);
 
       browser.test.assertEq(details.tabId, savedTabId, "correct tab ID");
@@ -173,8 +189,9 @@ function backgroundScript() {
 
   function onBeforeRedirect(details) {
     browser.test.log(`onBeforeRedirect ${details.url} -> ${details.redirectUrl}`);
+    checkRequestId(details);
     checkResourceType(details.type);
-    if (details.url.startsWith(BASE)) {
+    if (shouldRecord(details.url)) {
       recorded.beforeRedirect.push(details.url);
 
       browser.test.assertEq(details.tabId, savedTabId, "correct tab ID");
@@ -193,7 +210,8 @@ function backgroundScript() {
 
   function onRecord(kind, details) {
     checkResourceType(details.type);
-    if (details.url.startsWith(BASE)) {
+    checkRequestId(details);
+    if (shouldRecord(details.url)) {
       recorded[kind].push(details.url);
     }
   }
@@ -209,7 +227,10 @@ function backgroundScript() {
     // When resources are cached, the ip property is not present,
     // so only check for the ip property the first time around.
     if (checkCompleted && !completedUrls[kind].has(details.url)) {
-      browser.test.assertEq(details.ip, "127.0.0.1", "correct ip");
+      // We can only tell IPs for HTTP requests.
+      if (/^https?:/.test(details.url)) {
+        browser.test.assertEq(details.ip, "127.0.0.1", "correct ip");
+      }
       completedUrls[kind].add(details.url);
     }
   }
@@ -243,7 +264,7 @@ function* test_once(skipCompleted) {
         "webRequestBlocking",
       ],
     },
-    background: "(" + backgroundScript.toString() + ")()",
+    background: `const BASE = ${JSON.stringify(BASE)}; (${backgroundScript.toString()})()`,
   };
 
   let extension = ExtensionTestUtils.loadExtension(extensionData);
@@ -297,7 +318,7 @@ function* test_once(skipCompleted) {
   compareLists(recorded.beforeSendHeaders, expected_beforeSendHeaders, "beforeSendHeaders");
   compareLists(recorded.sendHeaders, expected_sendHeaders, "sendHeaders");
   compareLists(recorded.beforeRedirect, expected_redirect, "beforeRedirect");
-  compareLists(recorded.responseStarted, expected_complete, "responseStarted");
+  compareLists(recorded.responseStarted, expected_response, "responseStarted");
   compareLists(recorded.completed, expected_complete, "completed");
 
   yield extension.unload();
diff --git a/toolkit/modules/addons/MatchPattern.jsm b/toolkit/modules/addons/MatchPattern.jsm
index 7699d5b2e522..52404ad24e5e 100644
--- a/toolkit/modules/addons/MatchPattern.jsm
+++ b/toolkit/modules/addons/MatchPattern.jsm
@@ -15,7 +15,8 @@ this.EXPORTED_SYMBOLS = ["MatchPattern"];
 
 /* globals MatchPattern */
 
-const PERMITTED_SCHEMES = ["http", "https", "file", "ftp", "app"];
+const PERMITTED_SCHEMES = ["http", "https", "file", "ftp", "app", "data"];
+const PERMITTED_SCHEMES_REGEXP = PERMITTED_SCHEMES.join("|");
 
 // This function converts a glob pattern (containing * and possibly ?
 // as wildcards) to a regular expression.
@@ -42,7 +43,7 @@ function SingleMatchPattern(pat) {
   } else if (!pat) {
     this.schemes = [];
   } else {
-    let re = new RegExp("^(http|https|file|ftp|app|\\*)://(\\*|\\*\\.[^*/]+|[^*/]+|)(/.*)$");
+    let re = new RegExp(`^(${PERMITTED_SCHEMES_REGEXP}|\\*)://(\\*|\\*\\.[^*/]+|[^*/]+|)(/.*)$`);
     let match = re.exec(pat);
     if (!match) {
       Cu.reportError(`Invalid match pattern: '${pat}'`);
diff --git a/toolkit/modules/addons/WebRequest.jsm b/toolkit/modules/addons/WebRequest.jsm
index de2803fa86e4..f1c1ea21a08b 100644
--- a/toolkit/modules/addons/WebRequest.jsm
+++ b/toolkit/modules/addons/WebRequest.jsm
@@ -21,10 +21,44 @@ XPCOMUtils.defineLazyModuleGetter(this, "BrowserUtils",
 XPCOMUtils.defineLazyModuleGetter(this, "WebRequestCommon",
                                   "resource://gre/modules/WebRequestCommon.jsm");
 
-// TODO
-// Figure out how to handle requestId. Gecko seems to have no such thing. (Bug 1163862)
-// We also don't know the method for content policy. (Bug 1163862)
-// We don't even have a window ID for HTTP observer stuff. (Bug 1163861)
+function attachToChannel(channel, key, data) {
+  if (channel instanceof Ci.nsIWritablePropertyBag2) {
+    let wrapper = {value: data};
+    wrapper.wrappedJSObject = wrapper;
+    channel.setPropertyAsInterface(key, wrapper);
+  }
+}
+
+function extractFromChannel(channel, key) {
+  if (channel instanceof Ci.nsIPropertyBag2 && channel.hasKey(key)) {
+    let data = channel.get(key);
+    if (data && data.wrappedJSObject) {
+      data = data.wrappedJSObject;
+    }
+    return "value" in data ? data.value : data;
+  }
+  return null;
+}
+
+var RequestId = {
+  count: 1,
+  KEY: "mozilla.webRequest.requestId",
+  create(channel = null) {
+    let id = this.count++;
+    if (channel) {
+      attachToChannel(channel, this.KEY, id);
+    }
+    return id;
+  },
+
+  get(channel) {
+    return channel && extractFromChannel(channel, this.KEY) || this.create(channel);
+  },
+};
+
+function runLater(job) {
+  Services.tm.currentThread.dispatch(job, Ci.nsIEventTarget.DISPATCH_NORMAL);
+}
 
 function parseFilter(filter) {
   if (!filter) {
@@ -53,6 +87,8 @@ function parseExtra(extra, allowed) {
   return result;
 }
 
+var HttpObserverManager;
+
 var ContentPolicyManager = {
   policyData: new Map(),
   policies: new Map(),
@@ -77,32 +113,50 @@ var ContentPolicyManager = {
         continue;
       }
       let response = null;
+      let data = {
+        url: msg.data.url,
+        windowId: msg.data.windowId,
+        parentWindowId: msg.data.parentWindowId,
+        type: msg.data.type,
+        browser: browser,
+        requestId: RequestId.create(),
+      };
       try {
-        response = callback({
-          url: msg.data.url,
-          windowId: msg.data.windowId,
-          parentWindowId: msg.data.parentWindowId,
-          type: msg.data.type,
-          browser: browser,
-        });
+        response = callback(data);
+        if (response && response.cancel) {
+          return {cancel: true};
+        }
+
+        // FIXME: Need to handle redirection here. (Bug 1163862)
       } catch (e) {
         Cu.reportError(e);
+      } finally {
+        runLater(() => this.runChannelListener("onStop", data));
       }
-
-      if (response && response.cancel) {
-        return {cancel: true};
-      }
-
-      // FIXME: Need to handle redirection here. (Bug 1163862)
     }
 
     return {};
   },
 
+  runChannelListener(kind, data) {
+    let listeners = HttpObserverManager.listeners[kind];
+    let uri = BrowserUtils.makeURI(data.url);
+    let policyType = data.type;
+    for (let [callback, opts] of listeners.entries()) {
+      if (!HttpObserverManager.shouldRunListener(policyType, uri, opts.filter)) {
+        continue;
+      }
+      callback(data);
+    }
+  },
+
   addListener(callback, opts) {
+    // Clone opts, since we're going to modify them for IPC.
+    opts = Object.assign({}, opts);
     let id = this.nextId++;
     opts.id = id;
     if (opts.filter.urls) {
+      opts.filter = Object.assign({}, opts.filter);
       opts.filter.urls = opts.filter.urls.serialize();
     }
     Services.ppmm.broadcastAsyncMessage("WebRequest:AddContentPolicy", opts);
@@ -151,8 +205,6 @@ StartStopListener.prototype = {
   },
 };
 
-var HttpObserverManager;
-
 var ChannelEventSink = {
   _classDescription: "WebRequest channel event sink",
   _classID: Components.ID("115062f8-92f1-11e5-8b7f-080027b0f7ec"),
@@ -178,7 +230,7 @@ var ChannelEventSink = {
 
   // nsIChannelEventSink implementation
   asyncOnChannelRedirect(oldChannel, newChannel, flags, redirectCallback) {
-    Services.tm.currentThread.dispatch(() => redirectCallback.onRedirectVerifyCallback(Cr.NS_OK), Ci.nsIEventTarget.DISPATCH_NORMAL);
+    runLater(() => redirectCallback.onRedirectVerifyCallback(Cr.NS_OK));
     try {
       HttpObserverManager.onChannelReplaced(oldChannel, newChannel);
     } catch (e) {
@@ -203,6 +255,7 @@ HttpObserverManager = {
   redirectInitialized: false,
 
   listeners: {
+    opening: new Map(),
     modify: new Map(),
     afterModify: new Map(),
     headersReceived: new Map(),
@@ -212,7 +265,7 @@ HttpObserverManager = {
   },
 
   addOrRemove() {
-    let needModify = this.listeners.modify.size || this.listeners.afterModify.size;
+    let needModify = this.listeners.opening.size || this.listeners.modify.size || this.listeners.afterModify.size;
     if (needModify && !this.modifyInitialized) {
       this.modifyInitialized = true;
       Services.obs.addObserver(this, "http-on-modify-request", false);
@@ -289,13 +342,15 @@ HttpObserverManager = {
 
   observe(subject, topic, data) {
     let channel = subject.QueryInterface(Ci.nsIHttpChannel);
-
-    if (topic == "http-on-modify-request") {
-      this.modify(channel, topic, data);
-    } else if (topic == "http-on-examine-response" ||
-               topic == "http-on-examine-cached-response" ||
-               topic == "http-on-examine-merged-response") {
-      this.examine(channel, topic, data);
+    switch (topic) {
+      case "http-on-modify-request":
+        this.modify(channel, topic, data);
+        break;
+      case "http-on-examine-response":
+      case "http-on-examine-cached-response":
+      case "http-on-examine-merged-response":
+        this.examine(channel, topic, data);
+        break;
     }
   },
 
@@ -305,6 +360,9 @@ HttpObserverManager = {
   },
 
   runChannelListener(channel, loadContext, kind, extraData = null) {
+    if (channel.status === Cr.NS_ERROR_ABORT) {
+      return false;
+    }
     let listeners = this.listeners[kind];
     let browser = loadContext ? loadContext.topFrameElement : null;
     let loadInfo = channel.loadInfo;
@@ -326,6 +384,7 @@ HttpObserverManager = {
       }
 
       let data = {
+        requestId: RequestId.get(channel),
         url: channel.URI.spec,
         method: channel.requestMethod,
         browser: browser,
@@ -372,7 +431,7 @@ HttpObserverManager = {
         return true;
       }
       if (result.cancel) {
-        channel.cancel();
+        channel.cancel(Cr.NS_ERROR_ABORT);
         return false;
       }
       if (result.redirectUrl) {
@@ -407,7 +466,8 @@ HttpObserverManager = {
   modify(channel, topic, data) {
     let loadContext = this.getLoadContext(channel);
 
-    if (this.runChannelListener(channel, loadContext, "modify")) {
+    if (this.runChannelListener(channel, loadContext, "opening") &&
+        this.runChannelListener(channel, loadContext, "modify")) {
       this.runChannelListener(channel, loadContext, "afterModify");
     }
   },
@@ -450,9 +510,11 @@ var onBeforeRequest = {
     let opts = parseExtra(opt_extraInfoSpec, ["blocking"]);
     opts.filter = parseFilter(filter);
     ContentPolicyManager.addListener(callback, opts);
+    HttpObserverManager.addListener("opening", callback, opts);
   },
 
   removeListener(callback) {
+    HttpObserverManager.removeListener("opening", callback);
     ContentPolicyManager.removeListener(callback);
   },
 };
@@ -482,7 +544,7 @@ var onResponseStarted = new HttpEvent("onStart", ["responseHeaders"]);
 var onCompleted = new HttpEvent("onStop", ["responseHeaders"]);
 
 var WebRequest = {
-  // Handled via content policy.
+  // http-on-modify observer for HTTP(S), content policy for the other protocols (notably, data:)
   onBeforeRequest: onBeforeRequest,
 
   // http-on-modify observer.
diff --git a/toolkit/modules/addons/WebRequestContent.js b/toolkit/modules/addons/WebRequestContent.js
index 21a6e3e7bf2e..fc947be199a6 100644
--- a/toolkit/modules/addons/WebRequestContent.js
+++ b/toolkit/modules/addons/WebRequestContent.js
@@ -17,6 +17,8 @@ XPCOMUtils.defineLazyModuleGetter(this, "MatchPattern",
 XPCOMUtils.defineLazyModuleGetter(this, "WebRequestCommon",
                                   "resource://gre/modules/WebRequestCommon.jsm");
 
+const IS_HTTP = /^https?:/;
+
 var ContentPolicy = {
   _classDescription: "WebRequest content policy",
   _classID: Components.ID("938e5d24-9ccc-4b55-883e-c252a41f7ce9"),
@@ -78,6 +80,12 @@ var ContentPolicy = {
 
   shouldLoad(policyType, contentLocation, requestOrigin,
              node, mimeTypeGuess, extra, requestPrincipal) {
+    let url = contentLocation.spec;
+    if (IS_HTTP.test(url)) {
+      // We'll handle this in our parent process HTTP observer.
+      return Ci.nsIContentPolicy.ACCEPT;
+    }
+
     let block = false;
     let ids = [];
     for (let [id, {blocking, filter}] of this.contentPolicies.entries()) {
@@ -146,7 +154,7 @@ var ContentPolicy = {
     }
 
     let data = {ids,
-                url: contentLocation.spec,
+                url,
                 type: WebRequestCommon.typeForPolicyType(policyType),
                 windowId,
                 parentWindowId};
diff --git a/toolkit/modules/tests/browser/browser_WebRequest.js b/toolkit/modules/tests/browser/browser_WebRequest.js
index 82804ec645e7..5b1426a802e3 100644
--- a/toolkit/modules/tests/browser/browser_WebRequest.js
+++ b/toolkit/modules/tests/browser/browser_WebRequest.js
@@ -117,6 +117,7 @@ const expected_requested = [BASE + "/file_WebRequest_page1.html",
                             BASE + "/file_WebRequest_page2.html",
                             BASE + "/nonexistent_script_url.js",
                             BASE +  "/WebRequest_redirection.sjs",
+                            BASE + "/dummy_page.html",
                             BASE + "/xhr_resource"];
 
 const expected_sendHeaders = [BASE + "/file_WebRequest_page1.html",