Adding upstream version 1:115.7.0.upstream/1%115.7.0upstream

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

30 files changed, 5685 insertions, 0 deletions

diff --git a/devtools/shared/network-observer/ChannelMap.sys.mjs b/devtools/shared/network-observer/ChannelMap.sys.mjs
new file mode 100644
index 0000000000..3c54b1171a
--- /dev/null
+++ b/devtools/shared/network-observer/ChannelMap.sys.mjs
@@ -0,0 +1,129 @@
+/* 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/. */
+
+/**
+ * FinalizationRegistry callback, see
+ * https://searchfox.org/mozilla-central/source/js/src/builtin/FinalizationRegistryObject.h
+ *
+ * Will be invoked when the channel corresponding to the weak reference is
+ * "destroyed", at which point we can cleanup the corresponding entry in our
+ * regular map.
+ */
+function deleteIdFromRefMap({ refMap, id }) {
+  refMap.delete(id);
+}
+
+/**
+ * This object implements iterable weak map for HTTP channels tracked by
+ * the network observer.
+ *
+ * We can't use Map() for storing HTTP channel references since we don't
+ * know when we should remove the entry in it (it's wrong to do it in
+ * 'onTransactionClose' since it doesn't have to be the last platform
+ * notification for a given channel). We want the map to auto update
+ * when the channel is garbage collected.
+ *
+ * We can't use WeakMap() since searching for a value by the channel object
+ * isn't reliable (there might be different objects representing the same
+ * channel). We need to search by channel ID, but ID can't be used as key
+ * in WeakMap().
+ *
+ * So, this custom map solves aforementioned issues.
+ */
+export class ChannelMap {
+  #finalizationRegistry;
+  #refMap;
+  #weakMap;
+
+  constructor() {
+    // See https://searchfox.org/mozilla-central/source/js/src/builtin/FinalizationRegistryObject.h
+    this.#finalizationRegistry = new FinalizationRegistry(deleteIdFromRefMap);
+
+    // Map of channel id to a channel weak reference.
+    this.#refMap = new Map();
+
+    /**
+     * WeakMap from nsIChannel instances to objects which encapsulate ChannelMap
+     * values with the following structure:
+     * @property {Object} value
+     *     The actual value stored in this ChannelMap entry, which should relate
+     *     to this channel.
+     * @property {WeakRef} ref
+     *     Weak reference for the channel object which is the key of the entry.
+     */
+    this.#weakMap = new WeakMap();
+  }
+
+  /**
+   * Remove all entries from the ChannelMap.
+   */
+  clear() {
+    this.#refMap.clear();
+  }
+
+  /**
+   * Delete the entry for the provided channel from the underlying maps, if any.
+   * Note that this will only delete entries which were set for the exact same
+   * nsIChannel object, and will not attempt to look up entries by channel id.
+   *
+   * @param {nsIChannel} channel
+   *     The key to delete from the ChannelMap.
+   *
+   * @return {boolean}
+   *     True if an entry was deleted, false otherwise.
+   */
+  delete(channel) {
+    const entry = this.#weakMap.get(channel);
+    if (!entry) {
+      return false;
+    }
+
+    this.#weakMap.delete(channel);
+    this.#refMap.delete(channel.channelId);
+    this.#finalizationRegistry.unregister(entry.ref);
+    return true;
+  }
+
+  /**
+   * Retrieve a value stored in the ChannelMap by the provided channel.
+   *
+   * @param {nsIChannel} channel
+   *     The key to delete from the ChannelMap.
+   *
+   * @return {Object|null}
+   *     The value held for the provided channel.
+   *     Null if the channel did not match any known key.
+   */
+  get(channel) {
+    const ref = this.#refMap.get(channel.channelId);
+    const key = ref ? ref.deref() : null;
+    if (!key) {
+      return null;
+    }
+    const channelInfo = this.#weakMap.get(key);
+    return channelInfo ? channelInfo.value : null;
+  }
+
+  /**
+   * Adds or updates an entry in the ChannelMap for the provided channel.
+   *
+   * @param {nsIChannel} channel
+   *     The key of the entry to add or update.
+   * @param {Object} value
+   *     The value to add or update.
+   */
+  set(channel, value) {
+    const ref = new WeakRef(channel);
+    this.#weakMap.set(channel, { value, ref });
+    this.#refMap.set(channel.channelId, ref);
+    this.#finalizationRegistry.register(
+      channel,
+      {
+        refMap: this.#refMap,
+        id: channel.channelId,
+      },
+      ref
+    );
+  }
+}
diff --git a/devtools/shared/network-observer/NetworkHelper.sys.mjs b/devtools/shared/network-observer/NetworkHelper.sys.mjs
new file mode 100644
index 0000000000..3523c0854e
--- /dev/null
+++ b/devtools/shared/network-observer/NetworkHelper.sys.mjs
@@ -0,0 +1,917 @@
+/* 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/. */
+
+/*
+ * Software License Agreement (BSD License)
+ *
+ * Copyright (c) 2007, Parakey Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use of this software in source and binary forms,
+ * with or without modification, are permitted provided that the
+ * following conditions are met:
+ *
+ * * Redistributions of source code must retain the above
+ *   copyright notice, this list of conditions and the
+ *   following disclaimer.
+ *
+ * * Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the
+ *   following disclaimer in the documentation and/or other
+ *   materials provided with the distribution.
+ *
+ * * Neither the name of Parakey Inc. nor the names of its
+ *   contributors may be used to endorse or promote products
+ *   derived from this software without specific prior
+ *   written permission of Parakey Inc.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/*
+ * Creator:
+ *  Joe Hewitt
+ * Contributors
+ *  John J. Barton (IBM Almaden)
+ *  Jan Odvarko (Mozilla Corp.)
+ *  Max Stepanov (Aptana Inc.)
+ *  Rob Campbell (Mozilla Corp.)
+ *  Hans Hillen (Paciello Group, Mozilla)
+ *  Curtis Bartley (Mozilla Corp.)
+ *  Mike Collins (IBM Almaden)
+ *  Kevin Decker
+ *  Mike Ratcliffe (Comartis AG)
+ *  Hernan Rodríguez Colmeiro
+ *  Austin Andrews
+ *  Christoph Dorn
+ *  Steven Roussey (AppCenter Inc, Network54)
+ *  Mihai Sucan (Mozilla Corp.)
+ */
+
+import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  DevToolsInfaillibleUtils:
+    "resource://devtools/shared/DevToolsInfaillibleUtils.sys.mjs",
+});
+
+XPCOMUtils.defineLazyModuleGetters(lazy, {
+  NetUtil: "resource://gre/modules/NetUtil.jsm",
+});
+
+// It would make sense to put this in the above
+// ChromeUtils.defineESModuleGetters, but that doesn't seem to work.
+XPCOMUtils.defineLazyGetter(lazy, "certDecoder", () => {
+  const { parse, pemToDER } = ChromeUtils.importESModule(
+    "chrome://global/content/certviewer/certDecoder.mjs"
+  );
+  return { parse, pemToDER };
+});
+
+// "Lax", "Strict" and "None" are special values of the SameSite cookie
+// attribute that should not be translated.
+const COOKIE_SAMESITE = {
+  LAX: "Lax",
+  STRICT: "Strict",
+  NONE: "None",
+};
+
+/**
+ * Helper object for networking stuff.
+ *
+ * Most of the following functions have been taken from the Firebug source. They
+ * have been modified to match the Firefox coding rules.
+ */
+export var NetworkHelper = {
+  /**
+   * Converts text with a given charset to unicode.
+   *
+   * @param string text
+   *        Text to convert.
+   * @param string charset
+   *        Charset to convert the text to.
+   * @returns string
+   *          Converted text.
+   */
+  convertToUnicode(text, charset) {
+    // FIXME: We need to throw when text can't be converted e.g. the contents of
+    // an image. Until we have a way to do so with TextEncoder and TextDecoder
+    // we need to use nsIScriptableUnicodeConverter instead.
+    const conv = Cc[
+      "@mozilla.org/intl/scriptableunicodeconverter"
+    ].createInstance(Ci.nsIScriptableUnicodeConverter);
+    try {
+      conv.charset = charset || "UTF-8";
+      return conv.ConvertToUnicode(text);
+    } catch (ex) {
+      return text;
+    }
+  },
+
+  /**
+   * Reads all available bytes from stream and converts them to charset.
+   *
+   * @param nsIInputStream stream
+   * @param string charset
+   * @returns string
+   *          UTF-16 encoded string based on the content of stream and charset.
+   */
+  readAndConvertFromStream(stream, charset) {
+    let text = null;
+    try {
+      text = lazy.NetUtil.readInputStreamToString(stream, stream.available());
+      return this.convertToUnicode(text, charset);
+    } catch (err) {
+      return text;
+    }
+  },
+
+  /**
+   * Reads the posted text from request.
+   *
+   * @param nsIHttpChannel request
+   * @param string charset
+   *        The content document charset, used when reading the POSTed data.
+   * @returns string or null
+   *          Returns the posted string if it was possible to read from request
+   *          otherwise null.
+   */
+  readPostTextFromRequest(request, charset) {
+    if (request instanceof Ci.nsIUploadChannel) {
+      const iStream = request.uploadStream;
+
+      let isSeekableStream = false;
+      if (iStream instanceof Ci.nsISeekableStream) {
+        isSeekableStream = true;
+      }
+
+      let prevOffset;
+      if (isSeekableStream) {
+        prevOffset = iStream.tell();
+        iStream.seek(Ci.nsISeekableStream.NS_SEEK_SET, 0);
+      }
+
+      // Read data from the stream.
+      const text = this.readAndConvertFromStream(iStream, charset);
+
+      // Seek locks the file, so seek to the beginning only if necko hasn't
+      // read it yet, since necko doesn't seek to 0 before reading (at lest
+      // not till 459384 is fixed).
+      if (isSeekableStream && prevOffset == 0) {
+        iStream.seek(Ci.nsISeekableStream.NS_SEEK_SET, 0);
+      }
+      return text;
+    }
+    return null;
+  },
+
+  /**
+   * Reads the posted text from the page's cache.
+   *
+   * @param nsIDocShell docShell
+   * @param string charset
+   * @returns string or null
+   *          Returns the posted string if it was possible to read from
+   *          docShell otherwise null.
+   */
+  readPostTextFromPage(docShell, charset) {
+    const webNav = docShell.QueryInterface(Ci.nsIWebNavigation);
+    return this.readPostTextFromPageViaWebNav(webNav, charset);
+  },
+
+  /**
+   * Reads the posted text from the page's cache, given an nsIWebNavigation
+   * object.
+   *
+   * @param nsIWebNavigation webNav
+   * @param string charset
+   * @returns string or null
+   *          Returns the posted string if it was possible to read from
+   *          webNav, otherwise null.
+   */
+  readPostTextFromPageViaWebNav(webNav, charset) {
+    if (webNav instanceof Ci.nsIWebPageDescriptor) {
+      const descriptor = webNav.currentDescriptor;
+
+      if (
+        descriptor instanceof Ci.nsISHEntry &&
+        descriptor.postData &&
+        descriptor instanceof Ci.nsISeekableStream
+      ) {
+        descriptor.seek(Ci.nsISeekableStream.NS_SEEK_SET, 0);
+
+        return this.readAndConvertFromStream(descriptor, charset);
+      }
+    }
+    return null;
+  },
+
+  /**
+   * Gets the topFrameElement that is associated with request. This
+   * works in single-process and multiprocess contexts. It may cross
+   * the content/chrome boundary.
+   *
+   * @param nsIHttpChannel request
+   * @returns Element|null
+   *          The top frame element for the given request.
+   */
+  getTopFrameForRequest(request) {
+    try {
+      return this.getRequestLoadContext(request).topFrameElement;
+    } catch (ex) {
+      // request loadContext is not always available.
+    }
+    return null;
+  },
+
+  /**
+   * Gets the nsIDOMWindow that is associated with request.
+   *
+   * @param nsIHttpChannel request
+   * @returns nsIDOMWindow or null
+   */
+  getWindowForRequest(request) {
+    try {
+      return this.getRequestLoadContext(request).associatedWindow;
+    } catch (ex) {
+      // On some request notificationCallbacks and loadGroup are both null,
+      // so that we can't retrieve any nsILoadContext interface.
+      // Fallback on nsILoadInfo to try to retrieve the request's window.
+      // (this is covered by test_network_get.html and its CSS request)
+      return request.loadInfo.loadingDocument?.defaultView;
+    }
+  },
+
+  /**
+   * Gets the nsILoadContext that is associated with request.
+   *
+   * @param nsIHttpChannel request
+   * @returns nsILoadContext or null
+   */
+  getRequestLoadContext(request) {
+    try {
+      if (request.loadInfo.workerAssociatedBrowsingContext) {
+        return request.loadInfo.workerAssociatedBrowsingContext;
+      }
+    } catch (ex) {
+      // Ignore.
+    }
+    try {
+      return request.notificationCallbacks.getInterface(Ci.nsILoadContext);
+    } catch (ex) {
+      // Ignore.
+    }
+
+    try {
+      return request.loadGroup.notificationCallbacks.getInterface(
+        Ci.nsILoadContext
+      );
+    } catch (ex) {
+      // Ignore.
+    }
+
+    return null;
+  },
+
+  /**
+   * Determines whether the request has been made for the top level document.
+   *
+   * @param nsIHttpChannel request
+   * @returns Boolean True if the request represents the top level document.
+   */
+  isTopLevelLoad(request) {
+    if (request instanceof Ci.nsIChannel) {
+      const loadInfo = request.loadInfo;
+      if (loadInfo?.isTopLevelLoad) {
+        return request.loadFlags & Ci.nsIChannel.LOAD_DOCUMENT_URI;
+      }
+    }
+
+    return false;
+  },
+
+  /**
+   * Loads the content of url from the cache.
+   *
+   * @param string url
+   *        URL to load the cached content for.
+   * @param string charset
+   *        Assumed charset of the cached content. Used if there is no charset
+   *        on the channel directly.
+   * @param function callback
+   *        Callback that is called with the loaded cached content if available
+   *        or null if something failed while getting the cached content.
+   */
+  loadFromCache(url, charset, callback) {
+    const channel = lazy.NetUtil.newChannel({
+      uri: url,
+      loadUsingSystemPrincipal: true,
+    });
+
+    // Ensure that we only read from the cache and not the server.
+    channel.loadFlags =
+      Ci.nsIRequest.LOAD_FROM_CACHE |
+      Ci.nsICachingChannel.LOAD_ONLY_FROM_CACHE |
+      Ci.nsICachingChannel.LOAD_BYPASS_LOCAL_CACHE_IF_BUSY;
+
+    lazy.NetUtil.asyncFetch(channel, (inputStream, statusCode, request) => {
+      if (!Components.isSuccessCode(statusCode)) {
+        callback(null);
+        return;
+      }
+
+      // Try to get the encoding from the channel. If there is none, then use
+      // the passed assumed charset.
+      const requestChannel = request.QueryInterface(Ci.nsIChannel);
+      const contentCharset = requestChannel.contentCharset || charset;
+
+      // Read the content of the stream using contentCharset as encoding.
+      callback(this.readAndConvertFromStream(inputStream, contentCharset));
+    });
+  },
+
+  /**
+   * Parse a raw Cookie header value.
+   *
+   * @param string header
+   *        The raw Cookie header value.
+   * @return array
+   *         Array holding an object for each cookie. Each object holds the
+   *         following properties: name and value.
+   */
+  parseCookieHeader(header) {
+    const cookies = header.split(";");
+    const result = [];
+
+    cookies.forEach(function (cookie) {
+      const equal = cookie.indexOf("=");
+      const name = cookie.substr(0, equal);
+      const value = cookie.substr(equal + 1);
+      result.push({
+        name: unescape(name.trim()),
+        value: unescape(value.trim()),
+      });
+    });
+
+    return result;
+  },
+
+  /**
+   * Parse a raw Set-Cookie header value.
+   *
+   * @param array headers
+   *        Array of raw Set-Cookie header values.
+   * @return array
+   *         Array holding an object for each cookie. Each object holds the
+   *         following properties: name, value, secure (boolean), httpOnly
+   *         (boolean), path, domain, samesite and expires (ISO date string).
+   */
+  parseSetCookieHeaders(headers) {
+    function parseSameSiteAttribute(attribute) {
+      attribute = attribute.toLowerCase();
+      switch (attribute) {
+        case COOKIE_SAMESITE.LAX.toLowerCase():
+          return COOKIE_SAMESITE.LAX;
+        case COOKIE_SAMESITE.STRICT.toLowerCase():
+          return COOKIE_SAMESITE.STRICT;
+        default:
+          return COOKIE_SAMESITE.NONE;
+      }
+    }
+
+    const cookies = [];
+
+    for (const header of headers) {
+      const rawCookies = header.split(/\r\n|\n|\r/);
+
+      rawCookies.forEach(function (cookie) {
+        const equal = cookie.indexOf("=");
+        const name = unescape(cookie.substr(0, equal).trim());
+        const parts = cookie.substr(equal + 1).split(";");
+        const value = unescape(parts.shift().trim());
+
+        cookie = { name, value };
+
+        parts.forEach(function (part) {
+          part = part.trim();
+          if (part.toLowerCase() == "secure") {
+            cookie.secure = true;
+          } else if (part.toLowerCase() == "httponly") {
+            cookie.httpOnly = true;
+          } else if (part.indexOf("=") > -1) {
+            const pair = part.split("=");
+            pair[0] = pair[0].toLowerCase();
+            if (pair[0] == "path" || pair[0] == "domain") {
+              cookie[pair[0]] = pair[1];
+            } else if (pair[0] == "samesite") {
+              cookie[pair[0]] = parseSameSiteAttribute(pair[1]);
+            } else if (pair[0] == "expires") {
+              try {
+                pair[1] = pair[1].replace(/-/g, " ");
+                cookie.expires = new Date(pair[1]).toISOString();
+              } catch (ex) {
+                // Ignore.
+              }
+            }
+          }
+        });
+
+        cookies.push(cookie);
+      });
+    }
+
+    return cookies;
+  },
+
+  // This is a list of all the mime category maps jviereck could find in the
+  // firebug code base.
+  mimeCategoryMap: {
+    "text/plain": "txt",
+    "text/html": "html",
+    "text/xml": "xml",
+    "text/xsl": "txt",
+    "text/xul": "txt",
+    "text/css": "css",
+    "text/sgml": "txt",
+    "text/rtf": "txt",
+    "text/x-setext": "txt",
+    "text/richtext": "txt",
+    "text/javascript": "js",
+    "text/jscript": "txt",
+    "text/tab-separated-values": "txt",
+    "text/rdf": "txt",
+    "text/xif": "txt",
+    "text/ecmascript": "js",
+    "text/vnd.curl": "txt",
+    "text/x-json": "json",
+    "text/x-js": "txt",
+    "text/js": "txt",
+    "text/vbscript": "txt",
+    "view-source": "txt",
+    "view-fragment": "txt",
+    "application/xml": "xml",
+    "application/xhtml+xml": "xml",
+    "application/atom+xml": "xml",
+    "application/rss+xml": "xml",
+    "application/vnd.mozilla.maybe.feed": "xml",
+    "application/javascript": "js",
+    "application/x-javascript": "js",
+    "application/x-httpd-php": "txt",
+    "application/rdf+xml": "xml",
+    "application/ecmascript": "js",
+    "application/http-index-format": "txt",
+    "application/json": "json",
+    "application/x-js": "txt",
+    "application/x-mpegurl": "txt",
+    "application/vnd.apple.mpegurl": "txt",
+    "multipart/mixed": "txt",
+    "multipart/x-mixed-replace": "txt",
+    "image/svg+xml": "svg",
+    "application/octet-stream": "bin",
+    "image/jpeg": "image",
+    "image/jpg": "image",
+    "image/gif": "image",
+    "image/png": "image",
+    "image/bmp": "image",
+    "application/x-shockwave-flash": "flash",
+    "video/x-flv": "flash",
+    "audio/mpeg3": "media",
+    "audio/x-mpeg-3": "media",
+    "video/mpeg": "media",
+    "video/x-mpeg": "media",
+    "video/vnd.mpeg.dash.mpd": "xml",
+    "audio/ogg": "media",
+    "application/ogg": "media",
+    "application/x-ogg": "media",
+    "application/x-midi": "media",
+    "audio/midi": "media",
+    "audio/x-mid": "media",
+    "audio/x-midi": "media",
+    "music/crescendo": "media",
+    "audio/wav": "media",
+    "audio/x-wav": "media",
+    "text/json": "json",
+    "application/x-json": "json",
+    "application/json-rpc": "json",
+    "application/x-web-app-manifest+json": "json",
+    "application/manifest+json": "json",
+  },
+
+  /**
+   * Check if the given MIME type is a text-only MIME type.
+   *
+   * @param string mimeType
+   * @return boolean
+   */
+  isTextMimeType(mimeType) {
+    if (mimeType.indexOf("text/") == 0) {
+      return true;
+    }
+
+    // XML and JSON often come with custom MIME types, so in addition to the
+    // standard "application/xml" and "application/json", we also look for
+    // variants like "application/x-bigcorp+xml". For JSON we allow "+json" and
+    // "-json" as suffixes.
+    if (/^application\/\w+(?:[\.-]\w+)*(?:\+xml|[-+]json)$/.test(mimeType)) {
+      return true;
+    }
+
+    const category = this.mimeCategoryMap[mimeType] || null;
+    switch (category) {
+      case "txt":
+      case "js":
+      case "json":
+      case "css":
+      case "html":
+      case "svg":
+      case "xml":
+        return true;
+
+      default:
+        return false;
+    }
+  },
+
+  /**
+   * Takes a securityInfo object of nsIRequest, the nsIRequest itself and
+   * extracts security information from them.
+   *
+   * @param object securityInfo
+   *        The securityInfo object of a request. If null channel is assumed
+   *        to be insecure.
+   * @param object originAttributes
+   *        The OriginAttributes of the request.
+   * @param object httpActivity
+   *        The httpActivity object for the request with at least members
+   *        { private, hostname }.
+   * @param Map decodedCertificateCache
+   *        A Map of certificate fingerprints to decoded certificates, to avoid
+   *        repeatedly decoding previously-seen certificates.
+   *
+   * @return object
+   *         Returns an object containing following members:
+   *          - state: The security of the connection used to fetch this
+   *                   request. Has one of following string values:
+   *                    * "insecure": the connection was not secure (only http)
+   *                    * "weak": the connection has minor security issues
+   *                    * "broken": secure connection failed (e.g. expired cert)
+   *                    * "secure": the connection was properly secured.
+   *          If state == broken:
+   *            - errorMessage: error code string.
+   *          If state == secure:
+   *            - protocolVersion: one of TLSv1, TLSv1.1, TLSv1.2, TLSv1.3.
+   *            - cipherSuite: the cipher suite used in this connection.
+   *            - cert: information about certificate used in this connection.
+   *                    See parseCertificateInfo for the contents.
+   *            - hsts: true if host uses Strict Transport Security,
+   *                    false otherwise
+   *            - hpkp: true if host uses Public Key Pinning, false otherwise
+   *          If state == weak: Same as state == secure and
+   *            - weaknessReasons: list of reasons that cause the request to be
+   *                               considered weak. See getReasonsForWeakness.
+   */
+  async parseSecurityInfo(
+    securityInfo,
+    originAttributes,
+    httpActivity,
+    decodedCertificateCache
+  ) {
+    const info = {
+      state: "insecure",
+    };
+
+    // The request did not contain any security info.
+    if (!securityInfo) {
+      return info;
+    }
+
+    /**
+     * Different scenarios to consider here and how they are handled:
+     * - request is HTTP, the connection is not secure
+     *   => securityInfo is null
+     *      => state === "insecure"
+     *
+     * - request is HTTPS, the connection is secure
+     *   => .securityState has STATE_IS_SECURE flag
+     *      => state === "secure"
+     *
+     * - request is HTTPS, the connection has security issues
+     *   => .securityState has STATE_IS_INSECURE flag
+     *   => .errorCode is an NSS error code.
+     *      => state === "broken"
+     *
+     * - request is HTTPS, the connection was terminated before the security
+     *   could be validated
+     *   => .securityState has STATE_IS_INSECURE flag
+     *   => .errorCode is NOT an NSS error code.
+     *   => .errorMessage is not available.
+     *      => state === "insecure"
+     *
+     * - request is HTTPS but it uses a weak cipher or old protocol, see
+     *   https://hg.mozilla.org/mozilla-central/annotate/def6ed9d1c1a/
+     *   security/manager/ssl/nsNSSCallbacks.cpp#l1233
+     * - request is mixed content (which makes no sense whatsoever)
+     *   => .securityState has STATE_IS_BROKEN flag
+     *   => .errorCode is NOT an NSS error code
+     *   => .errorMessage is not available
+     *      => state === "weak"
+     */
+
+    const wpl = Ci.nsIWebProgressListener;
+    const NSSErrorsService = Cc["@mozilla.org/nss_errors_service;1"].getService(
+      Ci.nsINSSErrorsService
+    );
+    if (!NSSErrorsService.isNSSErrorCode(securityInfo.errorCode)) {
+      const state = securityInfo.securityState;
+
+      let uri = null;
+      if (httpActivity.channel?.URI) {
+        uri = httpActivity.channel.URI;
+      }
+      if (uri && !uri.schemeIs("https") && !uri.schemeIs("wss")) {
+        // it is not enough to look at the transport security info -
+        // schemes other than https and wss are subject to
+        // downgrade/etc at the scheme level and should always be
+        // considered insecure
+        info.state = "insecure";
+      } else if (state & wpl.STATE_IS_SECURE) {
+        // The connection is secure if the scheme is sufficient
+        info.state = "secure";
+      } else if (state & wpl.STATE_IS_BROKEN) {
+        // The connection is not secure, there was no error but there's some
+        // minor security issues.
+        info.state = "weak";
+        info.weaknessReasons = this.getReasonsForWeakness(state);
+      } else if (state & wpl.STATE_IS_INSECURE) {
+        // This was most likely an https request that was aborted before
+        // validation. Return info as info.state = insecure.
+        return info;
+      } else {
+        lazy.DevToolsInfaillibleUtils.reportException(
+          "NetworkHelper.parseSecurityInfo",
+          "Security state " + state + " has no known STATE_IS_* flags."
+        );
+        return info;
+      }
+
+      // Cipher suite.
+      info.cipherSuite = securityInfo.cipherName;
+
+      // Key exchange group name.
+      info.keaGroupName = securityInfo.keaGroupName;
+
+      // Certificate signature scheme.
+      info.signatureSchemeName = securityInfo.signatureSchemeName;
+
+      // Protocol version.
+      info.protocolVersion = this.formatSecurityProtocol(
+        securityInfo.protocolVersion
+      );
+
+      // Certificate.
+      info.cert = await this.parseCertificateInfo(
+        securityInfo.serverCert,
+        decodedCertificateCache
+      );
+
+      // Certificate transparency status.
+      info.certificateTransparency = securityInfo.certificateTransparencyStatus;
+
+      // HSTS and HPKP if available.
+      if (httpActivity.hostname) {
+        const sss = Cc["@mozilla.org/ssservice;1"].getService(
+          Ci.nsISiteSecurityService
+        );
+        const pkps = Cc[
+          "@mozilla.org/security/publickeypinningservice;1"
+        ].getService(Ci.nsIPublicKeyPinningService);
+
+        if (!uri) {
+          // isSecureURI only cares about the host, not the scheme.
+          const host = httpActivity.hostname;
+          uri = Services.io.newURI("https://" + host);
+        }
+
+        info.hsts = sss.isSecureURI(uri, originAttributes);
+        info.hpkp = pkps.hostHasPins(uri);
+      } else {
+        lazy.DevToolsInfaillibleUtils.reportException(
+          "NetworkHelper.parseSecurityInfo",
+          "Could not get HSTS/HPKP status as hostname is not available."
+        );
+        info.hsts = false;
+        info.hpkp = false;
+      }
+    } else {
+      // The connection failed.
+      info.state = "broken";
+      info.errorMessage = securityInfo.errorCodeString;
+    }
+
+    // These values can be unset in rare cases, e.g. when stashed connection
+    // data is deseralized from an older version of Firefox.
+    try {
+      info.usedEch = securityInfo.isAcceptedEch;
+    } catch {
+      info.usedEch = false;
+    }
+    try {
+      info.usedDelegatedCredentials = securityInfo.isDelegatedCredential;
+    } catch {
+      info.usedDelegatedCredentials = false;
+    }
+    info.usedOcsp = securityInfo.madeOCSPRequests;
+    info.usedPrivateDns = securityInfo.usedPrivateDNS;
+
+    return info;
+  },
+
+  /**
+   * Takes an nsIX509Cert and returns an object with certificate information.
+   *
+   * @param nsIX509Cert cert
+   *        The certificate to extract the information from.
+   * @param Map decodedCertificateCache
+   *        A Map of certificate fingerprints to decoded certificates, to avoid
+   *        repeatedly decoding previously-seen certificates.
+   * @return object
+   *         An object with following format:
+   *           {
+   *             subject: { commonName, organization, organizationalUnit },
+   *             issuer: { commonName, organization, organizationUnit },
+   *             validity: { start, end },
+   *             fingerprint: { sha1, sha256 }
+   *           }
+   */
+  async parseCertificateInfo(cert, decodedCertificateCache) {
+    function getDNComponent(dn, componentType) {
+      for (const [type, value] of dn.entries) {
+        if (type == componentType) {
+          return value;
+        }
+      }
+      return undefined;
+    }
+
+    const info = {};
+    if (cert) {
+      const certHash = cert.sha256Fingerprint;
+      let parsedCert = decodedCertificateCache.get(certHash);
+      if (!parsedCert) {
+        parsedCert = await lazy.certDecoder.parse(
+          lazy.certDecoder.pemToDER(cert.getBase64DERString())
+        );
+        decodedCertificateCache.set(certHash, parsedCert);
+      }
+      info.subject = {
+        commonName: getDNComponent(parsedCert.subject, "Common Name"),
+        organization: getDNComponent(parsedCert.subject, "Organization"),
+        organizationalUnit: getDNComponent(
+          parsedCert.subject,
+          "Organizational Unit"
+        ),
+      };
+
+      info.issuer = {
+        commonName: getDNComponent(parsedCert.issuer, "Common Name"),
+        organization: getDNComponent(parsedCert.issuer, "Organization"),
+        organizationUnit: getDNComponent(
+          parsedCert.issuer,
+          "Organizational Unit"
+        ),
+      };
+
+      info.validity = {
+        start: parsedCert.notBeforeUTC,
+        end: parsedCert.notAfterUTC,
+      };
+
+      info.fingerprint = {
+        sha1: parsedCert.fingerprint.sha1,
+        sha256: parsedCert.fingerprint.sha256,
+      };
+    } else {
+      lazy.DevToolsInfaillibleUtils.reportException(
+        "NetworkHelper.parseCertificateInfo",
+        "Secure connection established without certificate."
+      );
+    }
+
+    return info;
+  },
+
+  /**
+   * Takes protocolVersion of TransportSecurityInfo object and returns
+   * human readable description.
+   *
+   * @param Number version
+   *        One of nsITransportSecurityInfo version constants.
+   * @return string
+   *         One of TLSv1, TLSv1.1, TLSv1.2, TLSv1.3 if @param version
+   *         is valid, Unknown otherwise.
+   */
+  formatSecurityProtocol(version) {
+    switch (version) {
+      case Ci.nsITransportSecurityInfo.TLS_VERSION_1:
+        return "TLSv1";
+      case Ci.nsITransportSecurityInfo.TLS_VERSION_1_1:
+        return "TLSv1.1";
+      case Ci.nsITransportSecurityInfo.TLS_VERSION_1_2:
+        return "TLSv1.2";
+      case Ci.nsITransportSecurityInfo.TLS_VERSION_1_3:
+        return "TLSv1.3";
+      default:
+        lazy.DevToolsInfaillibleUtils.reportException(
+          "NetworkHelper.formatSecurityProtocol",
+          "protocolVersion " + version + " is unknown."
+        );
+        return "Unknown";
+    }
+  },
+
+  /**
+   * Takes the securityState bitfield and returns reasons for weak connection
+   * as an array of strings.
+   *
+   * @param Number state
+   *        nsITransportSecurityInfo.securityState.
+   *
+   * @return Array[String]
+   *         List of weakness reasons. A subset of { cipher } where
+   *         * cipher: The cipher suite is consireded to be weak (RC4).
+   */
+  getReasonsForWeakness(state) {
+    const wpl = Ci.nsIWebProgressListener;
+
+    // If there's non-fatal security issues the request has STATE_IS_BROKEN
+    // flag set. See https://hg.mozilla.org/mozilla-central/file/44344099d119
+    // /security/manager/ssl/nsNSSCallbacks.cpp#l1233
+    const reasons = [];
+
+    if (state & wpl.STATE_IS_BROKEN) {
+      const isCipher = state & wpl.STATE_USES_WEAK_CRYPTO;
+
+      if (isCipher) {
+        reasons.push("cipher");
+      }
+
+      if (!isCipher) {
+        lazy.DevToolsInfaillibleUtils.reportException(
+          "NetworkHelper.getReasonsForWeakness",
+          "STATE_IS_BROKEN without a known reason. Full state was: " + state
+        );
+      }
+    }
+
+    return reasons;
+  },
+
+  /**
+   * Parse a url's query string into its components
+   *
+   * @param string queryString
+   *        The query part of a url
+   * @return array
+   *         Array of query params {name, value}
+   */
+  parseQueryString(queryString) {
+    // Make sure there's at least one param available.
+    // Be careful here, params don't necessarily need to have values, so
+    // no need to verify the existence of a "=".
+    if (!queryString) {
+      return null;
+    }
+
+    // Turn the params string into an array containing { name: value } tuples.
+    const paramsArray = queryString
+      .replace(/^[?&]/, "")
+      .split("&")
+      .map(e => {
+        const param = e.split("=");
+        return {
+          name: param[0]
+            ? NetworkHelper.convertToUnicode(unescape(param[0]))
+            : "",
+          value: param[1]
+            ? NetworkHelper.convertToUnicode(unescape(param[1]))
+            : "",
+        };
+      });
+
+    return paramsArray;
+  },
+};
diff --git a/devtools/shared/network-observer/NetworkObserver.sys.mjs b/devtools/shared/network-observer/NetworkObserver.sys.mjs
new file mode 100644
index 0000000000..7137345393
--- /dev/null
+++ b/devtools/shared/network-observer/NetworkObserver.sys.mjs
@@ -0,0 +1,1397 @@
+/* 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/. */
+
+/**
+ * NetworkObserver is the main class in DevTools to observe network requests
+ * out of many events fired by the platform code.
+ */
+
+// Enable logging all platform events this module listen to
+const DEBUG_PLATFORM_EVENTS = false;
+
+const lazy = {};
+
+import { DevToolsInfaillibleUtils } from "resource://devtools/shared/DevToolsInfaillibleUtils.sys.mjs";
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  ChannelMap: "resource://devtools/shared/network-observer/ChannelMap.sys.mjs",
+  NetworkHelper:
+    "resource://devtools/shared/network-observer/NetworkHelper.sys.mjs",
+  NetworkOverride:
+    "resource://devtools/shared/network-observer/NetworkOverride.sys.mjs",
+  NetworkResponseListener:
+    "resource://devtools/shared/network-observer/NetworkResponseListener.sys.mjs",
+  NetworkThrottleManager:
+    "resource://devtools/shared/network-observer/NetworkThrottleManager.sys.mjs",
+  NetworkUtils:
+    "resource://devtools/shared/network-observer/NetworkUtils.sys.mjs",
+  wildcardToRegExp:
+    "resource://devtools/shared/network-observer/WildcardToRegexp.sys.mjs",
+});
+
+const gActivityDistributor = Cc[
+  "@mozilla.org/network/http-activity-distributor;1"
+].getService(Ci.nsIHttpActivityDistributor);
+
+function logPlatformEvent(eventName, channel, message = "") {
+  if (!DEBUG_PLATFORM_EVENTS) {
+    return;
+  }
+  dump(`[netmonitor] ${channel.channelId} - ${eventName} ${message}\n`);
+}
+
+// The maximum uint32 value.
+const PR_UINT32_MAX = 4294967295;
+
+const HTTP_TRANSACTION_CODES = {
+  0x5001: "REQUEST_HEADER",
+  0x5002: "REQUEST_BODY_SENT",
+  0x5003: "RESPONSE_START",
+  0x5004: "RESPONSE_HEADER",
+  0x5005: "RESPONSE_COMPLETE",
+  0x5006: "TRANSACTION_CLOSE",
+
+  0x4b0003: "STATUS_RESOLVING",
+  0x4b000b: "STATUS_RESOLVED",
+  0x4b0007: "STATUS_CONNECTING_TO",
+  0x4b0004: "STATUS_CONNECTED_TO",
+  0x4b0005: "STATUS_SENDING_TO",
+  0x4b000a: "STATUS_WAITING_FOR",
+  0x4b0006: "STATUS_RECEIVING_FROM",
+  0x4b000c: "STATUS_TLS_STARTING",
+  0x4b000d: "STATUS_TLS_ENDING",
+};
+
+const HTTP_DOWNLOAD_ACTIVITIES = [
+  gActivityDistributor.ACTIVITY_SUBTYPE_RESPONSE_START,
+  gActivityDistributor.ACTIVITY_SUBTYPE_RESPONSE_HEADER,
+  gActivityDistributor.ACTIVITY_SUBTYPE_RESPONSE_COMPLETE,
+  gActivityDistributor.ACTIVITY_SUBTYPE_TRANSACTION_CLOSE,
+];
+
+/**
+ * The network monitor uses the nsIHttpActivityDistributor to monitor network
+ * requests. The nsIObserverService is also used for monitoring
+ * http-on-examine-response notifications. All network request information is
+ * routed to the remote Web Console.
+ *
+ * @constructor
+ * @param {Object} options
+ * @param {Function(nsIChannel): boolean} options.ignoreChannelFunction
+ *        This function will be called for every detected channel to decide if it
+ *        should be monitored or not.
+ * @param {Function(NetworkEvent): owner} options.onNetworkEvent
+ *        This method is invoked once for every new network request with two
+ *        arguments:
+ *        - {Object} networkEvent: object created by NetworkUtils:createNetworkEvent,
+ *          containing initial network request information as an argument.
+ *        - {nsIChannel} channel: the channel for which the request was detected
+ *
+ *        `onNetworkEvent()` must return an "owner" object which holds several add*()
+ *        methods which are used to add further network request/response information.
+ */
+export class NetworkObserver {
+  /**
+   * Map of URL patterns to RegExp
+   *
+   * @type {Map}
+   */
+  #blockedURLs = new Map();
+
+  /**
+   * Map of URL to local file path in order to redirect URL
+   * to local file overrides.
+   *
+   * This will replace the content of some request with the content of local files.
+   */
+  #overrides = new Map();
+
+  /**
+   * Used by NetworkHelper.parseSecurityInfo to skip decoding known certificates.
+   *
+   * @type {Map}
+   */
+  #decodedCertificateCache = new Map();
+  /**
+   * See constructor argument of the same name.
+   *
+   * @type {Function}
+   */
+  #ignoreChannelFunction;
+  /**
+   * Used to store channels intercepted for service-worker requests.
+   *
+   * @type {WeakSet}
+   */
+  #interceptedChannels = new WeakSet();
+  /**
+   * Explicit flag to check if this observer was already destroyed.
+   *
+   * @type {boolean}
+   */
+  #isDestroyed = false;
+  /**
+   * See constructor argument of the same name.
+   *
+   * @type {Function}
+   */
+  #onNetworkEvent;
+  /**
+   * Object that holds the HTTP activity objects for ongoing requests.
+   *
+   * @type {ChannelMap}
+   */
+  #openRequests = new lazy.ChannelMap();
+  /**
+   * Network response bodies are piped through a buffer of the given size
+   * (in bytes).
+   *
+   * @type {Number}
+   */
+  #responsePipeSegmentSize = Services.prefs.getIntPref(
+    "network.buffer.cache.size"
+  );
+  /**
+   * Whether to save the bodies of network requests and responses.
+   *
+   * @type {boolean}
+   */
+  #saveRequestAndResponseBodies = true;
+  /**
+   * Throttling configuration, see constructor of NetworkThrottleManager
+   *
+   * @type {Object}
+   */
+  #throttleData = null;
+  /**
+   * NetworkThrottleManager instance, created when a valid throttleData is set.
+   * @type {NetworkThrottleManager}
+   */
+  #throttler = null;
+
+  constructor(options = {}) {
+    const { ignoreChannelFunction, onNetworkEvent } = options;
+    if (typeof ignoreChannelFunction !== "function") {
+      throw new Error(
+        `Expected "ignoreChannelFunction" to be a function, got ${ignoreChannelFunction} (${typeof ignoreChannelFunction})`
+      );
+    }
+
+    if (typeof onNetworkEvent !== "function") {
+      throw new Error(
+        `Expected "onNetworkEvent" to be a function, got ${onNetworkEvent} (${typeof onNetworkEvent})`
+      );
+    }
+
+    this.#ignoreChannelFunction = ignoreChannelFunction;
+    this.#onNetworkEvent = onNetworkEvent;
+
+    // Start all platform observers.
+    if (Services.appinfo.processType != Ci.nsIXULRuntime.PROCESS_TYPE_CONTENT) {
+      gActivityDistributor.addObserver(this);
+      Services.obs.addObserver(
+        this.#httpResponseExaminer,
+        "http-on-examine-response"
+      );
+      Services.obs.addObserver(
+        this.#httpResponseExaminer,
+        "http-on-examine-cached-response"
+      );
+      Services.obs.addObserver(
+        this.#httpModifyExaminer,
+        "http-on-modify-request"
+      );
+      Services.obs.addObserver(this.#httpStopRequest, "http-on-stop-request");
+    } else {
+      Services.obs.addObserver(
+        this.#httpFailedOpening,
+        "http-on-failed-opening-request"
+      );
+    }
+    // In child processes, only watch for service worker requests
+    // everything else only happens in the parent process
+    Services.obs.addObserver(
+      this.#serviceWorkerRequest,
+      "service-worker-synthesized-response"
+    );
+  }
+
+  setSaveRequestAndResponseBodies(save) {
+    this.#saveRequestAndResponseBodies = save;
+  }
+
+  getThrottleData() {
+    return this.#throttleData;
+  }
+
+  setThrottleData(value) {
+    this.#throttleData = value;
+    // Clear out any existing throttlers
+    this.#throttler = null;
+  }
+
+  #getThrottler() {
+    if (this.#throttleData !== null && this.#throttler === null) {
+      this.#throttler = new lazy.NetworkThrottleManager(this.#throttleData);
+    }
+    return this.#throttler;
+  }
+
+  #serviceWorkerRequest = DevToolsInfaillibleUtils.makeInfallible(
+    (subject, topic, data) => {
+      const channel = subject.QueryInterface(Ci.nsIHttpChannel);
+
+      if (this.#ignoreChannelFunction(channel)) {
+        return;
+      }
+
+      logPlatformEvent(topic, channel);
+
+      this.#interceptedChannels.add(subject);
+
+      // Service workers never fire http-on-examine-cached-response, so fake one.
+      this.#httpResponseExaminer(channel, "http-on-examine-cached-response");
+    }
+  );
+
+  /**
+   * Observes for http-on-failed-opening-request notification to catch any
+   * channels for which asyncOpen has synchronously failed.  This is the only
+   * place to catch early security check failures.
+   */
+  #httpFailedOpening = DevToolsInfaillibleUtils.makeInfallible(
+    (subject, topic) => {
+      if (
+        this.#isDestroyed ||
+        topic != "http-on-failed-opening-request" ||
+        !(subject instanceof Ci.nsIHttpChannel)
+      ) {
+        return;
+      }
+
+      const channel = subject.QueryInterface(Ci.nsIHttpChannel);
+      if (this.#ignoreChannelFunction(channel)) {
+        return;
+      }
+
+      logPlatformEvent(topic, channel);
+
+      // Ignore preload requests to avoid duplicity request entries in
+      // the Network panel. If a preload fails (for whatever reason)
+      // then the platform kicks off another 'real' request.
+      if (lazy.NetworkUtils.isPreloadRequest(channel)) {
+        return;
+      }
+
+      this.#httpResponseExaminer(subject, topic);
+    }
+  );
+
+  #httpStopRequest = DevToolsInfaillibleUtils.makeInfallible(
+    (subject, topic) => {
+      if (
+        this.#isDestroyed ||
+        topic != "http-on-stop-request" ||
+        !(subject instanceof Ci.nsIHttpChannel)
+      ) {
+        return;
+      }
+
+      const channel = subject.QueryInterface(Ci.nsIHttpChannel);
+      if (this.#ignoreChannelFunction(channel)) {
+        return;
+      }
+
+      logPlatformEvent(topic, channel);
+
+      const httpActivity = this.#createOrGetActivityObject(channel);
+      const serverTimings = this.#extractServerTimings(channel);
+
+      if (httpActivity.owner) {
+        // Try extracting server timings. Note that they will be sent to the client
+        // in the `_onTransactionClose` method together with network event timings.
+        httpActivity.owner.addServerTimings(serverTimings);
+
+        // If the owner isn't set we need to create the network event and send
+        // it to the client. This happens in case where:
+        // - the request has been blocked (e.g. CORS) and "http-on-stop-request" is the first notification.
+        // - the NetworkObserver is start *after* the request started and we only receive the http-stop notification,
+        //   but that doesn't mean the request is blocked, so check for its status.
+      } else if (Components.isSuccessCode(channel.status)) {
+        // Do not pass any blocked reason, as this request is just fine.
+        // Bug 1489217 - Prevent watching for this request response content,
+        // as this request is already running, this is too late to watch for it.
+        this.#createNetworkEvent(subject, { inProgressRequest: true });
+      } else {
+        // Handles any early blockings e.g by Web Extensions or by CORS
+        const { blockingExtension, blockedReason } =
+          lazy.NetworkUtils.getBlockedReason(channel);
+        this.#createNetworkEvent(subject, { blockedReason, blockingExtension });
+      }
+    }
+  );
+
+  /**
+   * Check if the current channel has its content being overriden
+   * by the content of some local file.
+   */
+  #checkForContentOverride(channel) {
+    const overridePath = this.#overrides.get(channel.URI.spec);
+    if (!overridePath) {
+      return false;
+    }
+
+    dump(" Override " + channel.URI.spec + " to " + overridePath + "\n");
+    try {
+      lazy.NetworkOverride.overrideChannelWithFilePath(channel, overridePath);
+    } catch (e) {
+      dump("Exception while trying to override request content: " + e + "\n");
+    }
+
+    return true;
+  }
+
+  /**
+   * Observe notifications for the http-on-examine-response topic, coming from
+   * the nsIObserverService.
+   *
+   * @private
+   * @param nsIHttpChannel subject
+   * @param string topic
+   * @returns void
+   */
+  #httpResponseExaminer = DevToolsInfaillibleUtils.makeInfallible(
+    (subject, topic) => {
+      // The httpResponseExaminer is used to retrieve the uncached response
+      // headers.
+      if (
+        this.#isDestroyed ||
+        (topic != "http-on-examine-response" &&
+          topic != "http-on-examine-cached-response" &&
+          topic != "http-on-failed-opening-request") ||
+        !(subject instanceof Ci.nsIHttpChannel) ||
+        !(subject instanceof Ci.nsIClassifiedChannel)
+      ) {
+        return;
+      }
+
+      const blockedOrFailed = topic === "http-on-failed-opening-request";
+
+      subject.QueryInterface(Ci.nsIClassifiedChannel);
+      const channel = subject.QueryInterface(Ci.nsIHttpChannel);
+
+      if (this.#ignoreChannelFunction(channel)) {
+        return;
+      }
+
+      logPlatformEvent(
+        topic,
+        subject,
+        blockedOrFailed
+          ? "blockedOrFailed:" + channel.loadInfo.requestBlockingReason
+          : channel.responseStatus
+      );
+
+      this.#checkForContentOverride(channel);
+
+      channel.QueryInterface(Ci.nsIHttpChannelInternal);
+
+      let httpActivity = this.#createOrGetActivityObject(channel);
+      if (topic === "http-on-examine-cached-response") {
+        // Service worker requests emits cached-response notification on non-e10s,
+        // and we fake one on e10s.
+        const fromServiceWorker = this.#interceptedChannels.has(channel);
+        this.#interceptedChannels.delete(channel);
+
+        // If this is a cached response (which are also emitted by service worker requests),
+        // there never was a request event so we need to construct one here
+        // so the frontend gets all the expected events.
+        if (!httpActivity.owner) {
+          httpActivity = this.#createNetworkEvent(channel, {
+            fromCache: !fromServiceWorker,
+            fromServiceWorker,
+          });
+        }
+
+        // We need to send the request body to the frontend for
+        // the faked (cached/service worker request) event.
+        this.#prepareRequestBody(httpActivity);
+        this.#sendRequestBody(httpActivity);
+
+        // There also is never any timing events, so we can fire this
+        // event with zeroed out values.
+        const timings = this.#setupHarTimings(httpActivity);
+
+        const serverTimings = this.#extractServerTimings(httpActivity.channel);
+        httpActivity.owner.addEventTimings(
+          timings.total,
+          timings.timings,
+          timings.offsets,
+          serverTimings
+        );
+      } else if (topic === "http-on-failed-opening-request") {
+        const { blockedReason } = lazy.NetworkUtils.getBlockedReason(channel);
+        this.#createNetworkEvent(channel, { blockedReason });
+      }
+
+      if (httpActivity.owner) {
+        httpActivity.owner.addResponseStart({
+          channel: httpActivity.channel,
+          fromCache: httpActivity.fromCache || httpActivity.fromServiceWorker,
+          rawHeaders: httpActivity.responseRawHeaders,
+        });
+      }
+    }
+  );
+
+  /**
+   * Observe notifications for the http-on-modify-request topic, coming from
+   * the nsIObserverService.
+   *
+   * @private
+   * @param nsIHttpChannel aSubject
+   * @returns void
+   */
+  #httpModifyExaminer = DevToolsInfaillibleUtils.makeInfallible(subject => {
+    const throttler = this.#getThrottler();
+    if (throttler) {
+      const channel = subject.QueryInterface(Ci.nsIHttpChannel);
+      if (this.#ignoreChannelFunction(channel)) {
+        return;
+      }
+      logPlatformEvent("http-on-modify-request", channel);
+
+      // Read any request body here, before it is throttled.
+      const httpActivity = this.#createOrGetActivityObject(channel);
+      this.#prepareRequestBody(httpActivity);
+      throttler.manageUpload(channel);
+    }
+  });
+
+  /**
+   * A helper function for observeActivity.  This does whatever work
+   * is required by a particular http activity event.  Arguments are
+   * the same as for observeActivity.
+   */
+  #dispatchActivity(
+    httpActivity,
+    channel,
+    activityType,
+    activitySubtype,
+    timestamp,
+    extraSizeData,
+    extraStringData
+  ) {
+    // Store the time information for this activity subtype.
+    if (activitySubtype in HTTP_TRANSACTION_CODES) {
+      const stage = HTTP_TRANSACTION_CODES[activitySubtype];
+      if (stage in httpActivity.timings) {
+        httpActivity.timings[stage].last = timestamp;
+      } else {
+        httpActivity.timings[stage] = {
+          first: timestamp,
+          last: timestamp,
+        };
+      }
+    }
+
+    switch (activitySubtype) {
+      case gActivityDistributor.ACTIVITY_SUBTYPE_REQUEST_BODY_SENT:
+        this.#prepareRequestBody(httpActivity);
+        this.#sendRequestBody(httpActivity);
+        break;
+      case gActivityDistributor.ACTIVITY_SUBTYPE_RESPONSE_HEADER:
+        httpActivity.responseRawHeaders = extraStringData;
+        httpActivity.headersSize = extraStringData.length;
+        break;
+      case gActivityDistributor.ACTIVITY_SUBTYPE_TRANSACTION_CLOSE:
+        this.#onTransactionClose(httpActivity);
+        break;
+      default:
+        break;
+    }
+  }
+
+  getActivityTypeString(activityType, activitySubtype) {
+    if (
+      activityType === Ci.nsIHttpActivityObserver.ACTIVITY_TYPE_SOCKET_TRANSPORT
+    ) {
+      for (const name in Ci.nsISocketTransport) {
+        if (Ci.nsISocketTransport[name] === activitySubtype) {
+          return "SOCKET_TRANSPORT:" + name;
+        }
+      }
+    } else if (
+      activityType === Ci.nsIHttpActivityObserver.ACTIVITY_TYPE_HTTP_TRANSACTION
+    ) {
+      for (const name in Ci.nsIHttpActivityObserver) {
+        if (Ci.nsIHttpActivityObserver[name] === activitySubtype) {
+          return "HTTP_TRANSACTION:" + name.replace("ACTIVITY_SUBTYPE_", "");
+        }
+      }
+    }
+    return "unexpected-activity-types:" + activityType + ":" + activitySubtype;
+  }
+
+  /**
+   * Begin observing HTTP traffic that originates inside the current tab.
+   *
+   * @see https://developer.mozilla.org/en/XPCOM_Interface_Reference/nsIHttpActivityObserver
+   *
+   * @param nsIHttpChannel channel
+   * @param number activityType
+   * @param number activitySubtype
+   * @param number timestamp
+   * @param number extraSizeData
+   * @param string extraStringData
+   */
+  observeActivity = DevToolsInfaillibleUtils.makeInfallible(function (
+    channel,
+    activityType,
+    activitySubtype,
+    timestamp,
+    extraSizeData,
+    extraStringData
+  ) {
+    if (
+      this.#isDestroyed ||
+      (activityType != gActivityDistributor.ACTIVITY_TYPE_HTTP_TRANSACTION &&
+        activityType != gActivityDistributor.ACTIVITY_TYPE_SOCKET_TRANSPORT)
+    ) {
+      return;
+    }
+
+    if (
+      !(channel instanceof Ci.nsIHttpChannel) ||
+      !(channel instanceof Ci.nsIClassifiedChannel)
+    ) {
+      return;
+    }
+
+    channel = channel.QueryInterface(Ci.nsIHttpChannel);
+    channel = channel.QueryInterface(Ci.nsIClassifiedChannel);
+
+    if (DEBUG_PLATFORM_EVENTS) {
+      logPlatformEvent(
+        this.getActivityTypeString(activityType, activitySubtype),
+        channel
+      );
+    }
+
+    if (
+      activitySubtype == gActivityDistributor.ACTIVITY_SUBTYPE_REQUEST_HEADER
+    ) {
+      this.#onRequestHeader(channel, timestamp, extraStringData);
+      return;
+    }
+
+    // Iterate over all currently ongoing requests. If channel can't
+    // be found within them, then exit this function.
+    const httpActivity = this.#findActivityObject(channel);
+    if (!httpActivity) {
+      return;
+    }
+
+    // If we're throttling, we must not report events as they arrive
+    // from platform, but instead let the throttler emit the events
+    // after some time has elapsed.
+    if (
+      httpActivity.downloadThrottle &&
+      HTTP_DOWNLOAD_ACTIVITIES.includes(activitySubtype)
+    ) {
+      const callback = this.#dispatchActivity.bind(this);
+      httpActivity.downloadThrottle.addActivityCallback(
+        callback,
+        httpActivity,
+        channel,
+        activityType,
+        activitySubtype,
+        timestamp,
+        extraSizeData,
+        extraStringData
+      );
+    } else {
+      this.#dispatchActivity(
+        httpActivity,
+        channel,
+        activityType,
+        activitySubtype,
+        timestamp,
+        extraSizeData,
+        extraStringData
+      );
+    }
+  });
+
+  /**
+   * Craft the "event" object passed to the Watcher class in order
+   * to instantiate the NetworkEventActor.
+   *
+   * /!\ This method does many other important things:
+   * - Cancel requests blocked by DevTools
+   * - Fetch request headers/cookies
+   * - Set a few attributes on http activity object
+   * - Register listener to record response content
+   */
+  #createNetworkEvent(
+    channel,
+    {
+      timestamp,
+      rawHeaders,
+      fromCache,
+      fromServiceWorker,
+      blockedReason,
+      blockingExtension,
+      inProgressRequest,
+    }
+  ) {
+    const httpActivity = this.#createOrGetActivityObject(channel);
+
+    if (timestamp) {
+      httpActivity.timings.REQUEST_HEADER = {
+        first: timestamp,
+        last: timestamp,
+      };
+    }
+
+    if (blockedReason === undefined && this.#shouldBlockChannel(channel)) {
+      // Check the request URL with ones manually blocked by the user in DevTools.
+      // If it's meant to be blocked, we cancel the request and annotate the event.
+      channel.cancel(Cr.NS_BINDING_ABORTED);
+      blockedReason = "devtools";
+    }
+
+    httpActivity.owner = this.#onNetworkEvent(
+      {
+        timestamp,
+        fromCache,
+        fromServiceWorker,
+        rawHeaders,
+        blockedReason,
+        blockingExtension,
+        discardRequestBody: !this.#saveRequestAndResponseBodies,
+        discardResponseBody: !this.#saveRequestAndResponseBodies,
+      },
+      channel
+    );
+    httpActivity.fromCache = fromCache || fromServiceWorker;
+
+    // Bug 1489217 - Avoid watching for response content for blocked or in-progress requests
+    // as it can't be observed and would throw if we try.
+    if (blockedReason === undefined && !inProgressRequest) {
+      this.#setupResponseListener(httpActivity, {
+        fromCache,
+        fromServiceWorker,
+      });
+    }
+
+    return httpActivity;
+  }
+
+  /**
+   * Handler for ACTIVITY_SUBTYPE_REQUEST_HEADER. When a request starts the
+   * headers are sent to the server. This method creates the |httpActivity|
+   * object where we store the request and response information that is
+   * collected through its lifetime.
+   *
+   * @private
+   * @param nsIHttpChannel channel
+   * @param number timestamp
+   * @param string rawHeaders
+   * @return void
+   */
+  #onRequestHeader(channel, timestamp, rawHeaders) {
+    if (this.#ignoreChannelFunction(channel)) {
+      return;
+    }
+
+    this.#createNetworkEvent(channel, {
+      timestamp,
+      rawHeaders,
+    });
+  }
+
+  /**
+   * Check if the provided channel should be blocked given the current
+   * blocked URLs configured for this network observer.
+   */
+  #shouldBlockChannel(channel) {
+    for (const regexp of this.#blockedURLs.values()) {
+      if (regexp.test(channel.URI.spec)) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  /**
+   * Find an HTTP activity object for the channel.
+   *
+   * @param nsIHttpChannel channel
+   *        The HTTP channel whose activity object we want to find.
+   * @return object
+   *        The HTTP activity object, or null if it is not found.
+   */
+  #findActivityObject(channel) {
+    return this.#openRequests.get(channel);
+  }
+
+  /**
+   * Find an existing HTTP activity object, or create a new one. This
+   * object is used for storing all the request and response
+   * information.
+   *
+   * This is a HAR-like object. Conformance to the spec is not guaranteed at
+   * this point.
+   *
+   * @see http://www.softwareishard.com/blog/har-12-spec
+   * @param nsIHttpChannel channel
+   *        The HTTP channel for which the HTTP activity object is created.
+   * @return object
+   *         The new HTTP activity object.
+   */
+  #createOrGetActivityObject(channel) {
+    let httpActivity = this.#findActivityObject(channel);
+    if (!httpActivity) {
+      const win = lazy.NetworkHelper.getWindowForRequest(channel);
+      const charset = win ? win.document.characterSet : null;
+
+      // Most of the data needed from the channel is only available via the
+      // nsIHttpChannelInternal interface.
+      channel.QueryInterface(Ci.nsIHttpChannelInternal);
+
+      httpActivity = {
+        // The nsIChannel for which this activity object was created.
+        channel,
+        // See #prepareRequestBody()
+        charset,
+        // The postData sent by this request.
+        sentBody: null,
+        // The URL for the current channel.
+        url: channel.URI.spec,
+        // The encoded response body size.
+        bodySize: 0,
+        // The response headers size.
+        headersSize: 0,
+        // needed for host specific security info
+        hostname: channel.URI.host,
+        discardRequestBody: !this.#saveRequestAndResponseBodies,
+        discardResponseBody: !this.#saveRequestAndResponseBodies,
+        // internal timing information, see observeActivity()
+        timings: {},
+        // the activity owner which is notified when changes happen
+        owner: null,
+      };
+
+      this.#openRequests.set(channel, httpActivity);
+    }
+
+    return httpActivity;
+  }
+
+  /**
+   * Block a request based on certain filtering options.
+   *
+   * Currently, exact URL match or URL patterns are supported.
+   */
+  blockRequest(filter) {
+    if (!filter || !filter.url) {
+      // In the future, there may be other types of filters, such as domain.
+      // For now, ignore anything other than URL.
+      return;
+    }
+
+    this.#addBlockedUrl(filter.url);
+  }
+
+  /**
+   * Unblock a request based on certain filtering options.
+   *
+   * Currently, exact URL match or URL patterns are supported.
+   */
+  unblockRequest(filter) {
+    if (!filter || !filter.url) {
+      // In the future, there may be other types of filters, such as domain.
+      // For now, ignore anything other than URL.
+      return;
+    }
+
+    this.#blockedURLs.delete(filter.url);
+  }
+
+  /**
+   * Updates the list of blocked request strings
+   *
+   * This match will be a (String).includes match, not an exact URL match
+   */
+  setBlockedUrls(urls) {
+    urls = urls || [];
+    this.#blockedURLs = new Map();
+    urls.forEach(url => this.#addBlockedUrl(url));
+  }
+
+  #addBlockedUrl(url) {
+    this.#blockedURLs.set(url, lazy.wildcardToRegExp(url));
+  }
+
+  /**
+   * Returns a list of blocked requests
+   * Useful as blockedURLs is mutated by both console & netmonitor
+   */
+  getBlockedUrls() {
+    return this.#blockedURLs.keys();
+  }
+
+  override(url, path) {
+    this.#overrides.set(url, path);
+  }
+
+  removeOverride(url) {
+    this.#overrides.delete(url);
+  }
+
+  /**
+   * Setup the network response listener for the given HTTP activity. The
+   * NetworkResponseListener is responsible for storing the response body.
+   *
+   * @private
+   * @param object httpActivity
+   *        The HTTP activity object we are tracking.
+   */
+  #setupResponseListener(httpActivity, { fromCache, fromServiceWorker }) {
+    const channel = httpActivity.channel;
+    channel.QueryInterface(Ci.nsITraceableChannel);
+
+    if (!fromCache) {
+      const throttler = this.#getThrottler();
+      if (throttler) {
+        httpActivity.downloadThrottle = throttler.manage(channel);
+      }
+    }
+
+    // The response will be written into the outputStream of this pipe.
+    // This allows us to buffer the data we are receiving and read it
+    // asynchronously.
+    // Both ends of the pipe must be blocking.
+    const sink = Cc["@mozilla.org/pipe;1"].createInstance(Ci.nsIPipe);
+
+    // The streams need to be blocking because this is required by the
+    // stream tee.
+    sink.init(false, false, this.#responsePipeSegmentSize, PR_UINT32_MAX, null);
+
+    // Add listener for the response body.
+    const newListener = new lazy.NetworkResponseListener(
+      httpActivity,
+      this.#decodedCertificateCache,
+      fromServiceWorker
+    );
+
+    // Remember the input stream, so it isn't released by GC.
+    newListener.inputStream = sink.inputStream;
+    newListener.sink = sink;
+
+    const tee = Cc["@mozilla.org/network/stream-listener-tee;1"].createInstance(
+      Ci.nsIStreamListenerTee
+    );
+
+    const originalListener = channel.setNewListener(tee);
+
+    tee.init(originalListener, sink.outputStream, newListener);
+  }
+
+  /**
+   * Handler for ACTIVITY_SUBTYPE_REQUEST_BODY_SENT. Read and record the request
+   * body here. It will be available in addResponseStart.
+   *
+   * @private
+   * @param object httpActivity
+   *        The HTTP activity object we are working with.
+   */
+  #prepareRequestBody(httpActivity) {
+    // Return early if we don't need the request body, or if we've
+    // already found it.
+    if (httpActivity.discardRequestBody || httpActivity.sentBody !== null) {
+      return;
+    }
+
+    let sentBody = lazy.NetworkHelper.readPostTextFromRequest(
+      httpActivity.channel,
+      httpActivity.charset
+    );
+
+    if (
+      sentBody !== null &&
+      this.window &&
+      httpActivity.url == this.window.location.href
+    ) {
+      // If the request URL is the same as the current page URL, then
+      // we can try to get the posted text from the page directly.
+      // This check is necessary as otherwise the
+      //   lazy.NetworkHelper.readPostTextFromPageViaWebNav()
+      // function is called for image requests as well but these
+      // are not web pages and as such don't store the posted text
+      // in the cache of the webpage.
+      const webNav = this.window.docShell.QueryInterface(Ci.nsIWebNavigation);
+      sentBody = lazy.NetworkHelper.readPostTextFromPageViaWebNav(
+        webNav,
+        httpActivity.charset
+      );
+    }
+
+    if (sentBody !== null) {
+      httpActivity.sentBody = sentBody;
+    }
+  }
+
+  /**
+   * Handler for ACTIVITY_SUBTYPE_TRANSACTION_CLOSE. This method updates the HAR
+   * timing information on the HTTP activity object and clears the request
+   * from the list of known open requests.
+   *
+   * @private
+   * @param object httpActivity
+   *        The HTTP activity object we work with.
+   */
+  #onTransactionClose(httpActivity) {
+    if (httpActivity.owner) {
+      const result = this.#setupHarTimings(httpActivity);
+      const serverTimings = this.#extractServerTimings(httpActivity.channel);
+
+      httpActivity.owner.addEventTimings(
+        result.total,
+        result.timings,
+        result.offsets,
+        serverTimings
+      );
+    }
+  }
+
+  #getBlockedTiming(timings) {
+    if (timings.STATUS_RESOLVING && timings.STATUS_CONNECTING_TO) {
+      return timings.STATUS_RESOLVING.first - timings.REQUEST_HEADER.first;
+    } else if (timings.STATUS_SENDING_TO) {
+      return timings.STATUS_SENDING_TO.first - timings.REQUEST_HEADER.first;
+    }
+
+    return -1;
+  }
+
+  #getDnsTiming(timings) {
+    if (timings.STATUS_RESOLVING && timings.STATUS_RESOLVED) {
+      return timings.STATUS_RESOLVED.last - timings.STATUS_RESOLVING.first;
+    }
+
+    return -1;
+  }
+
+  #getConnectTiming(timings) {
+    if (timings.STATUS_CONNECTING_TO && timings.STATUS_CONNECTED_TO) {
+      return (
+        timings.STATUS_CONNECTED_TO.last - timings.STATUS_CONNECTING_TO.first
+      );
+    }
+
+    return -1;
+  }
+
+  #getReceiveTiming(timings) {
+    if (timings.RESPONSE_START && timings.RESPONSE_COMPLETE) {
+      return timings.RESPONSE_COMPLETE.last - timings.RESPONSE_START.first;
+    }
+
+    return -1;
+  }
+
+  #getWaitTiming(timings) {
+    if (timings.RESPONSE_START) {
+      return (
+        timings.RESPONSE_START.first -
+        (timings.REQUEST_BODY_SENT || timings.STATUS_SENDING_TO).last
+      );
+    }
+
+    return -1;
+  }
+
+  #getSslTiming(timings) {
+    if (timings.STATUS_TLS_STARTING && timings.STATUS_TLS_ENDING) {
+      return timings.STATUS_TLS_ENDING.last - timings.STATUS_TLS_STARTING.first;
+    }
+
+    return -1;
+  }
+
+  #getSendTiming(timings) {
+    if (timings.STATUS_SENDING_TO) {
+      return timings.STATUS_SENDING_TO.last - timings.STATUS_SENDING_TO.first;
+    } else if (timings.REQUEST_HEADER && timings.REQUEST_BODY_SENT) {
+      return timings.REQUEST_BODY_SENT.last - timings.REQUEST_HEADER.first;
+    }
+
+    return -1;
+  }
+
+  #getDataFromTimedChannel(timedChannel) {
+    const lookUpArr = [
+      "tcpConnectEndTime",
+      "connectStartTime",
+      "connectEndTime",
+      "secureConnectionStartTime",
+      "domainLookupEndTime",
+      "domainLookupStartTime",
+    ];
+
+    return lookUpArr.reduce((prev, prop) => {
+      const propName = prop + "Tc";
+      return {
+        ...prev,
+        [propName]: (() => {
+          if (!timedChannel) {
+            return 0;
+          }
+
+          const value = timedChannel[prop];
+
+          if (
+            value != 0 &&
+            timedChannel.asyncOpenTime &&
+            value < timedChannel.asyncOpenTime
+          ) {
+            return 0;
+          }
+
+          return value;
+        })(),
+      };
+    }, {});
+  }
+
+  #getSecureConnectionStartTimeInfo(timings) {
+    let secureConnectionStartTime = 0;
+    let secureConnectionStartTimeRelative = false;
+
+    if (timings.STATUS_TLS_STARTING && timings.STATUS_TLS_ENDING) {
+      if (timings.STATUS_CONNECTING_TO) {
+        secureConnectionStartTime =
+          timings.STATUS_TLS_STARTING.first -
+          timings.STATUS_CONNECTING_TO.first;
+      }
+
+      if (secureConnectionStartTime < 0) {
+        secureConnectionStartTime = 0;
+      }
+      secureConnectionStartTimeRelative = true;
+    }
+
+    return {
+      secureConnectionStartTime,
+      secureConnectionStartTimeRelative,
+    };
+  }
+
+  #getStartSendingTimeInfo(timings, connectStartTimeTc) {
+    let startSendingTime = 0;
+    let startSendingTimeRelative = false;
+
+    if (timings.STATUS_SENDING_TO) {
+      if (timings.STATUS_CONNECTING_TO) {
+        startSendingTime =
+          timings.STATUS_SENDING_TO.first - timings.STATUS_CONNECTING_TO.first;
+        startSendingTimeRelative = true;
+      } else if (connectStartTimeTc != 0) {
+        startSendingTime = timings.STATUS_SENDING_TO.first - connectStartTimeTc;
+        startSendingTimeRelative = true;
+      }
+
+      if (startSendingTime < 0) {
+        startSendingTime = 0;
+      }
+    }
+    return { startSendingTime, startSendingTimeRelative };
+  }
+
+  /**
+   * Update the HTTP activity object to include timing information as in the HAR
+   * spec. The HTTP activity object holds the raw timing information in
+   * |timings| - these are timings stored for each activity notification. The
+   * HAR timing information is constructed based on these lower level
+   * data.
+   *
+   * @param {Object} httpActivity
+   *     The HTTP activity object we are working with.
+   * @return {Object}
+   *     This object holds three properties:
+   *     - {Object} offsets: the timings computed as offsets from the initial
+   *     request start time.
+   *     - {Object} timings: the HAR timings object
+   *     - {number} total: the total time for all of the request and response
+   */
+  #setupHarTimings(httpActivity) {
+    if (httpActivity.fromCache) {
+      // If it came from the browser cache, we have no timing
+      // information and these should all be 0
+      return {
+        total: 0,
+        timings: {
+          blocked: 0,
+          dns: 0,
+          ssl: 0,
+          connect: 0,
+          send: 0,
+          wait: 0,
+          receive: 0,
+        },
+        offsets: {
+          blocked: 0,
+          dns: 0,
+          ssl: 0,
+          connect: 0,
+          send: 0,
+          wait: 0,
+          receive: 0,
+        },
+      };
+    }
+
+    const timings = httpActivity.timings;
+    const harTimings = {};
+    // If the TCP Fast Open option or tls1.3 0RTT is used tls and data can
+    // be dispatched in SYN packet and not after tcp socket is connected.
+    // To demostrate this properly we will calculated TLS and send start time
+    // relative to CONNECTING_TO.
+    // Similary if 0RTT is used, data can be sent as soon as a TLS handshake
+    // starts.
+
+    harTimings.blocked = this.#getBlockedTiming(timings);
+    // DNS timing information is available only in when the DNS record is not
+    // cached.
+    harTimings.dns = this.#getDnsTiming(timings);
+    harTimings.connect = this.#getConnectTiming(timings);
+    harTimings.ssl = this.#getSslTiming(timings);
+
+    let { secureConnectionStartTime, secureConnectionStartTimeRelative } =
+      this.#getSecureConnectionStartTimeInfo(timings);
+
+    // sometimes the connection information events are attached to a speculative
+    // channel instead of this one, but necko might glue them back together in the
+    // nsITimedChannel interface used by Resource and Navigation Timing
+    const timedChannel = httpActivity.channel.QueryInterface(
+      Ci.nsITimedChannel
+    );
+
+    const {
+      tcpConnectEndTimeTc,
+      connectStartTimeTc,
+      connectEndTimeTc,
+      secureConnectionStartTimeTc,
+      domainLookupEndTimeTc,
+      domainLookupStartTimeTc,
+    } = this.#getDataFromTimedChannel(timedChannel);
+
+    if (
+      harTimings.connect <= 0 &&
+      timedChannel &&
+      tcpConnectEndTimeTc != 0 &&
+      connectStartTimeTc != 0
+    ) {
+      harTimings.connect = tcpConnectEndTimeTc - connectStartTimeTc;
+      if (secureConnectionStartTimeTc != 0) {
+        harTimings.ssl = connectEndTimeTc - secureConnectionStartTimeTc;
+        secureConnectionStartTime =
+          secureConnectionStartTimeTc - connectStartTimeTc;
+        secureConnectionStartTimeRelative = true;
+      } else {
+        harTimings.ssl = -1;
+      }
+    } else if (
+      timedChannel &&
+      timings.STATUS_TLS_STARTING &&
+      secureConnectionStartTimeTc != 0
+    ) {
+      // It can happen that TCP Fast Open actually have not sent any data and
+      // timings.STATUS_TLS_STARTING.first value will be corrected in
+      // timedChannel.secureConnectionStartTime
+      if (secureConnectionStartTimeTc > timings.STATUS_TLS_STARTING.first) {
+        // TCP Fast Open actually did not sent any data.
+        harTimings.ssl = connectEndTimeTc - secureConnectionStartTimeTc;
+        secureConnectionStartTimeRelative = false;
+      }
+    }
+
+    if (
+      harTimings.dns <= 0 &&
+      timedChannel &&
+      domainLookupEndTimeTc != 0 &&
+      domainLookupStartTimeTc != 0
+    ) {
+      harTimings.dns = domainLookupEndTimeTc - domainLookupStartTimeTc;
+    }
+
+    harTimings.send = this.#getSendTiming(timings);
+    harTimings.wait = this.#getWaitTiming(timings);
+    harTimings.receive = this.#getReceiveTiming(timings);
+    let { startSendingTime, startSendingTimeRelative } =
+      this.#getStartSendingTimeInfo(timings, connectStartTimeTc);
+
+    if (secureConnectionStartTimeRelative) {
+      const time = Math.max(Math.round(secureConnectionStartTime / 1000), -1);
+      secureConnectionStartTime = time;
+    }
+    if (startSendingTimeRelative) {
+      const time = Math.max(Math.round(startSendingTime / 1000), -1);
+      startSendingTime = time;
+    }
+
+    const ot = this.#calculateOffsetAndTotalTime(
+      harTimings,
+      secureConnectionStartTime,
+      startSendingTimeRelative,
+      secureConnectionStartTimeRelative,
+      startSendingTime
+    );
+    return {
+      total: ot.total,
+      timings: harTimings,
+      offsets: ot.offsets,
+    };
+  }
+
+  #extractServerTimings(channel) {
+    if (!channel || !channel.serverTiming) {
+      return null;
+    }
+
+    const serverTimings = new Array(channel.serverTiming.length);
+
+    for (let i = 0; i < channel.serverTiming.length; ++i) {
+      const { name, duration, description } =
+        channel.serverTiming.queryElementAt(i, Ci.nsIServerTiming);
+      serverTimings[i] = { name, duration, description };
+    }
+
+    return serverTimings;
+  }
+
+  #convertTimeToMs(timing) {
+    return Math.max(Math.round(timing / 1000), -1);
+  }
+
+  #calculateOffsetAndTotalTime(
+    harTimings,
+    secureConnectionStartTime,
+    startSendingTimeRelative,
+    secureConnectionStartTimeRelative,
+    startSendingTime
+  ) {
+    let totalTime = 0;
+    for (const timing in harTimings) {
+      const time = this.#convertTimeToMs(harTimings[timing]);
+      harTimings[timing] = time;
+      if (time > -1 && timing != "connect" && timing != "ssl") {
+        totalTime += time;
+      }
+    }
+
+    // connect, ssl and send times can be overlapped.
+    if (startSendingTimeRelative) {
+      totalTime += startSendingTime;
+    } else if (secureConnectionStartTimeRelative) {
+      totalTime += secureConnectionStartTime;
+      totalTime += harTimings.ssl;
+    }
+
+    const offsets = {};
+    offsets.blocked = 0;
+    offsets.dns = harTimings.blocked;
+    offsets.connect = offsets.dns + harTimings.dns;
+    if (secureConnectionStartTimeRelative) {
+      offsets.ssl = offsets.connect + secureConnectionStartTime;
+    } else {
+      offsets.ssl = offsets.connect + harTimings.connect;
+    }
+    if (startSendingTimeRelative) {
+      offsets.send = offsets.connect + startSendingTime;
+      if (!secureConnectionStartTimeRelative) {
+        offsets.ssl = offsets.send - harTimings.ssl;
+      }
+    } else {
+      offsets.send = offsets.ssl + harTimings.ssl;
+    }
+    offsets.wait = offsets.send + harTimings.send;
+    offsets.receive = offsets.wait + harTimings.wait;
+
+    return {
+      total: totalTime,
+      offsets,
+    };
+  }
+
+  #sendRequestBody(httpActivity) {
+    if (httpActivity.sentBody !== null) {
+      const limit = Services.prefs.getIntPref(
+        "devtools.netmonitor.requestBodyLimit"
+      );
+      const size = httpActivity.sentBody.length;
+      if (size > limit && limit > 0) {
+        httpActivity.sentBody = httpActivity.sentBody.substr(0, limit);
+      }
+      httpActivity.owner.addRequestPostData({
+        text: httpActivity.sentBody,
+        size,
+      });
+      httpActivity.sentBody = null;
+    }
+  }
+
+  /*
+   * Clears the open requests channel map.
+   */
+  clear() {
+    this.#openRequests.clear();
+  }
+
+  /**
+   * Suspend observer activity. This is called when the Network monitor actor stops
+   * listening.
+   */
+  destroy() {
+    if (Services.appinfo.processType != Ci.nsIXULRuntime.PROCESS_TYPE_CONTENT) {
+      gActivityDistributor.removeObserver(this);
+      Services.obs.removeObserver(
+        this.#httpResponseExaminer,
+        "http-on-examine-response"
+      );
+      Services.obs.removeObserver(
+        this.#httpResponseExaminer,
+        "http-on-examine-cached-response"
+      );
+      Services.obs.removeObserver(
+        this.#httpModifyExaminer,
+        "http-on-modify-request"
+      );
+      Services.obs.removeObserver(
+        this.#httpStopRequest,
+        "http-on-stop-request"
+      );
+    } else {
+      Services.obs.removeObserver(
+        this.#httpFailedOpening,
+        "http-on-failed-opening-request"
+      );
+    }
+
+    Services.obs.removeObserver(
+      this.#serviceWorkerRequest,
+      "service-worker-synthesized-response"
+    );
+
+    this.#ignoreChannelFunction = null;
+    this.#onNetworkEvent = null;
+    this.#throttler = null;
+    this.#decodedCertificateCache.clear();
+    this.clear();
+
+    this.#isDestroyed = true;
+  }
+}
diff --git a/devtools/shared/network-observer/NetworkOverride.sys.mjs b/devtools/shared/network-observer/NetworkOverride.sys.mjs
new file mode 100644
index 0000000000..a7857bcd76
--- /dev/null
+++ b/devtools/shared/network-observer/NetworkOverride.sys.mjs
@@ -0,0 +1,70 @@
+/* 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 modules focuses on redirecting requests to a particular local file.
+ */
+
+import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
+
+const { NetUtil } = ChromeUtils.import("resource://gre/modules/NetUtil.jsm");
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  FileUtils: "resource://gre/modules/FileUtils.sys.mjs",
+});
+
+XPCOMUtils.defineLazyServiceGetter(
+  lazy,
+  "mimeService",
+  "@mozilla.org/mime;1",
+  "nsIMIMEService"
+);
+
+function readFile(file) {
+  const fstream = Cc["@mozilla.org/network/file-input-stream;1"].createInstance(
+    Ci.nsIFileInputStream
+  );
+  fstream.init(file, -1, 0, 0);
+  const data = NetUtil.readInputStreamToString(fstream, fstream.available());
+  fstream.close();
+  return data;
+}
+
+/**
+ * Given an in-flight channel, we will force to replace the content of this request
+ * with the content of a local file.
+ *
+ * @param {nsIHttpChannel} channel
+ *        The request to replace content for.
+ * @param {String} path
+ *        The absolute path to the local file to read content from.
+ */
+function overrideChannelWithFilePath(channel, path) {
+  // For JS it isn't important, but for HTML we ought to set the right content type on the data URI.
+  let mimeType = "";
+  try {
+    // getTypeFromURI will throw if there is no extension at the end of the URI
+    mimeType = lazy.mimeService.getTypeFromURI(channel.URI);
+  } catch (e) {}
+
+  // Redirect to a data: URI as we can't redirect to file:// URI
+  // without many security issues. We are leveraging the `allowInsecureRedirectToDataURI`
+  // attribute used by WebExtension.
+  const file = lazy.FileUtils.File(path);
+  const data = readFile(file);
+  const redirectURI = Services.io.newURI(
+    `data:${mimeType};base64,${btoa(data)}`
+  );
+
+  channel.redirectTo(redirectURI);
+
+  // Prevents having CORS exception and various issues because of redirecting to data: URI.
+  channel.loadInfo.allowInsecureRedirectToDataURI = true;
+}
+
+export const NetworkOverride = {
+  overrideChannelWithFilePath,
+};
diff --git a/devtools/shared/network-observer/NetworkResponseListener.sys.mjs b/devtools/shared/network-observer/NetworkResponseListener.sys.mjs
new file mode 100644
index 0000000000..23246c73de
--- /dev/null
+++ b/devtools/shared/network-observer/NetworkResponseListener.sys.mjs
@@ -0,0 +1,609 @@
+/* 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/. */
+
+import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  getResponseCacheObject:
+    "resource://devtools/shared/platform/CacheEntry.sys.mjs",
+  NetworkHelper:
+    "resource://devtools/shared/network-observer/NetworkHelper.sys.mjs",
+  NetworkUtils:
+    "resource://devtools/shared/network-observer/NetworkUtils.sys.mjs",
+});
+
+XPCOMUtils.defineLazyModuleGetters(lazy, {
+  NetUtil: "resource://gre/modules/NetUtil.jsm",
+});
+
+// Network logging
+
+/**
+ * The network response listener implements the nsIStreamListener and
+ * nsIRequestObserver interfaces. This is used within the NetworkObserver feature
+ * to get the response body of the request.
+ *
+ * The code is mostly based on code listings from:
+ *
+ *   http://www.softwareishard.com/blog/firebug/
+ *      nsitraceablechannel-intercept-http-traffic/
+ *
+ * @constructor
+ * @param {Object} httpActivity
+ *        HttpActivity object associated with this request. See NetworkObserver
+ *        more information.
+ * @param {Map} decodedCertificateCache
+ *        A Map of certificate fingerprints to decoded certificates, to avoid
+ *        repeatedly decoding previously-seen certificates.
+ */
+export class NetworkResponseListener {
+  /**
+   * The compressed and encoded response body size. Will progressively increase
+   * until the full response is received.
+   *
+   * @type {Number}
+   */
+  #bodySize = 0;
+  /**
+   * The uncompressed, decoded response body size.
+   *
+   * @type {Number}
+   */
+  #decodedBodySize = 0;
+  /**
+   * nsIStreamListener created by nsIStreamConverterService.asyncConvertData
+   *
+   * @type {nsIStreamListener}
+   */
+  #converter = null;
+  /**
+   * See constructor argument of the same name.
+   *
+   * @type {Map}
+   */
+  #decodedCertificateCache;
+  /**
+   * Is the channel from a service worker
+   *
+   * @type {boolean}
+   */
+  #fromServiceWorker;
+  /**
+   * See constructor argument of the same name.
+   *
+   * @type {Object}
+   */
+  #httpActivity;
+  /**
+   * Set from sink.inputStream, mainly to prevent GC.
+   *
+   * @type {nsIInputStream}
+   */
+  #inputStream = null;
+  /**
+   * Explicit flag to check if this listener was already destroyed.
+   *
+   * @type {boolean}
+   */
+  #isDestroyed = false;
+  /**
+   * Internal promise used to hold the completion of #getSecurityInfo.
+   *
+   * @type {Promise}
+   */
+  #onSecurityInfo = null;
+  /**
+   * Offset for the onDataAvailable calls where we pass the data from our pipe
+   * to the converter.
+   *
+   * @type {Number}
+   */
+  #offset = 0;
+  /**
+   * Stores the received data as a string.
+   *
+   * @type {string}
+   */
+  #receivedData = "";
+  /**
+   * The nsIRequest we are started for.
+   *
+   * @type {nsIRequest}
+   */
+  #request = null;
+  /**
+   * The response will be written into the outputStream of this nsIPipe.
+   * Both ends of the pipe must be blocking.
+   *
+   * @type {nsIPipe}
+   */
+  #sink = null;
+  /**
+   * Indicates if the response had a size greater than response body limit.
+   *
+   * @type {boolean}
+   */
+  #truncated = false;
+  /**
+   * Backup for existing notificationCallbacks set on the monitored channel.
+   * Initialized in the constructor.
+   *
+   * @type {Object}
+   */
+  #wrappedNotificationCallbacks;
+
+  constructor(httpActivity, decodedCertificateCache, fromServiceWorker) {
+    this.#httpActivity = httpActivity;
+    this.#decodedCertificateCache = decodedCertificateCache;
+    this.#fromServiceWorker = fromServiceWorker;
+
+    // Note that this is really only needed for the non-e10s case.
+    // See bug 1309523.
+    const channel = this.#httpActivity.channel;
+    // If the channel already had notificationCallbacks, hold them here
+    // internally so that we can forward getInterface requests to that object.
+    this.#wrappedNotificationCallbacks = channel.notificationCallbacks;
+    channel.notificationCallbacks = this;
+  }
+
+  set inputStream(inputStream) {
+    this.#inputStream = inputStream;
+  }
+
+  set sink(sink) {
+    this.#sink = sink;
+  }
+
+  // nsIInterfaceRequestor implementation
+
+  /**
+   * This object implements nsIProgressEventSink, but also needs to forward
+   * interface requests to the notification callbacks of other objects.
+   */
+  getInterface(iid) {
+    if (iid.equals(Ci.nsIProgressEventSink)) {
+      return this;
+    }
+    if (this.#wrappedNotificationCallbacks) {
+      return this.#wrappedNotificationCallbacks.getInterface(iid);
+    }
+    throw Components.Exception("", Cr.NS_ERROR_NO_INTERFACE);
+  }
+
+  /**
+   * Forward notifications for interfaces this object implements, in case other
+   * objects also implemented them.
+   */
+  #forwardNotification(iid, method, args) {
+    if (!this.#wrappedNotificationCallbacks) {
+      return;
+    }
+    try {
+      const impl = this.#wrappedNotificationCallbacks.getInterface(iid);
+      impl[method].apply(impl, args);
+    } catch (e) {
+      if (e.result != Cr.NS_ERROR_NO_INTERFACE) {
+        throw e;
+      }
+    }
+  }
+
+  /**
+   * Set the async listener for the given nsIAsyncInputStream. This allows us to
+   * wait asynchronously for any data coming from the stream.
+   *
+   * @param nsIAsyncInputStream stream
+   *        The input stream from where we are waiting for data to come in.
+   * @param nsIInputStreamCallback listener
+   *        The input stream callback you want. This is an object that must have
+   *        the onInputStreamReady() method. If the argument is null, then the
+   *        current callback is removed.
+   * @return void
+   */
+  setAsyncListener(stream, listener) {
+    // Asynchronously wait for the stream to be readable or closed.
+    stream.asyncWait(listener, 0, 0, Services.tm.mainThread);
+  }
+
+  /**
+   * Stores the received data, if request/response body logging is enabled. It
+   * also does limit the number of stored bytes, based on the
+   * `devtools.netmonitor.responseBodyLimit` pref.
+   *
+   * Learn more about nsIStreamListener at:
+   * https://developer.mozilla.org/en/XPCOM_Interface_Reference/nsIStreamListener
+   *
+   * @param nsIRequest request
+   * @param nsISupports context
+   * @param nsIInputStream inputStream
+   * @param unsigned long offset
+   * @param unsigned long count
+   */
+  onDataAvailable(request, inputStream, offset, count) {
+    const data = lazy.NetUtil.readInputStreamToString(inputStream, count);
+
+    this.#decodedBodySize += count;
+
+    if (!this.#httpActivity.discardResponseBody) {
+      const limit = Services.prefs.getIntPref(
+        "devtools.netmonitor.responseBodyLimit"
+      );
+      if (this.#receivedData.length <= limit || limit == 0) {
+        this.#receivedData += lazy.NetworkHelper.convertToUnicode(
+          data,
+          request.contentCharset
+        );
+      }
+      if (this.#receivedData.length > limit && limit > 0) {
+        this.#receivedData = this.#receivedData.substr(0, limit);
+        this.#truncated = true;
+      }
+    }
+  }
+
+  /**
+   * See documentation at
+   * https://developer.mozilla.org/En/NsIRequestObserver
+   *
+   * @param nsIRequest request
+   * @param nsISupports context
+   */
+  onStartRequest(request) {
+    request = request.QueryInterface(Ci.nsIChannel);
+    // Converter will call this again, we should just ignore that.
+    if (this.#request) {
+      return;
+    }
+
+    this.#request = request;
+    this.#onSecurityInfo = this.#getSecurityInfo();
+    // We need to track the offset for the onDataAvailable calls where
+    // we pass the data from our pipe to the converter.
+    this.#offset = 0;
+
+    const channel = this.#request;
+
+    // Bug 1372115 - We should load bytecode cached requests from cache as the actual
+    // channel content is going to be optimized data that reflects platform internals
+    // instead of the content user expects (i.e. content served by HTTP server)
+    // Note that bytecode cached is one example, there may be wasm or other usecase in
+    // future.
+    let isOptimizedContent = false;
+    try {
+      if (channel instanceof Ci.nsICacheInfoChannel) {
+        isOptimizedContent = channel.alternativeDataType;
+      }
+    } catch (e) {
+      // Accessing `alternativeDataType` for some SW requests throws.
+    }
+    if (isOptimizedContent) {
+      let charset;
+      try {
+        charset = this.#request.contentCharset;
+      } catch (e) {
+        // Accessing the charset sometimes throws NS_ERROR_NOT_AVAILABLE when
+        // reloading the page
+      }
+      if (!charset) {
+        charset = this.#httpActivity.charset;
+      }
+      lazy.NetworkHelper.loadFromCache(
+        this.#httpActivity.url,
+        charset,
+        this.#onComplete.bind(this)
+      );
+      return;
+    }
+
+    // In the multi-process mode, the conversion happens on the child
+    // side while we can only monitor the channel on the parent
+    // side. If the content is gzipped, we have to unzip it
+    // ourself. For that we use the stream converter services.  Do not
+    // do that for Service workers as they are run in the child
+    // process.
+    if (
+      !this.#fromServiceWorker &&
+      channel instanceof Ci.nsIEncodedChannel &&
+      channel.contentEncodings &&
+      !channel.applyConversion
+    ) {
+      const encodingHeader = channel.getResponseHeader("Content-Encoding");
+      const scs = Cc["@mozilla.org/streamConverters;1"].getService(
+        Ci.nsIStreamConverterService
+      );
+      const encodings = encodingHeader.split(/\s*\t*,\s*\t*/);
+      let nextListener = this;
+      const acceptedEncodings = [
+        "gzip",
+        "deflate",
+        "br",
+        "x-gzip",
+        "x-deflate",
+      ];
+      for (const i in encodings) {
+        // There can be multiple conversions applied
+        const enc = encodings[i].toLowerCase();
+        if (acceptedEncodings.indexOf(enc) > -1) {
+          this.#converter = scs.asyncConvertData(
+            enc,
+            "uncompressed",
+            nextListener,
+            null
+          );
+          nextListener = this.#converter;
+        }
+      }
+      if (this.#converter) {
+        this.#converter.onStartRequest(this.#request, null);
+      }
+    }
+    // Asynchronously wait for the data coming from the request.
+    this.setAsyncListener(this.#sink.inputStream, this);
+  }
+
+  /**
+   * Parse security state of this request and report it to the client.
+   */
+  async #getSecurityInfo() {
+    // Many properties of the securityInfo (e.g., the server certificate or HPKP
+    // status) are not available in the content process and can't be even touched safely,
+    // because their C++ getters trigger assertions. This function is called in content
+    // process for synthesized responses from service workers, in the parent otherwise.
+    if (Services.appinfo.processType == Ci.nsIXULRuntime.PROCESS_TYPE_CONTENT) {
+      return;
+    }
+
+    // Take the security information from the original nsIHTTPChannel instead of
+    // the nsIRequest received in onStartRequest. If response to this request
+    // was a redirect from http to https, the request object seems to contain
+    // security info for the https request after redirect.
+    const secinfo = this.#httpActivity.channel.securityInfo;
+    const info = await lazy.NetworkHelper.parseSecurityInfo(
+      secinfo,
+      this.#request.loadInfo.originAttributes,
+      this.#httpActivity,
+      this.#decodedCertificateCache
+    );
+    let isRacing = false;
+    try {
+      const channel = this.#httpActivity.channel;
+      if (channel instanceof Ci.nsICacheInfoChannel) {
+        isRacing = channel.isRacing();
+      }
+    } catch (err) {
+      // See the following bug for more details:
+      // https://bugzilla.mozilla.org/show_bug.cgi?id=1582589
+    }
+
+    this.#httpActivity.owner.addSecurityInfo(info, isRacing);
+  }
+
+  /**
+   * Fetches cache information from CacheEntry
+   * @private
+   */
+  async #fetchCacheInformation() {
+    // TODO: This method is async and #httpActivity is nullified in the #destroy
+    // method of this class. Backup httpActivity to avoid errors here.
+    const httpActivity = this.#httpActivity;
+    const cacheEntry = await lazy.getResponseCacheObject(this.#request);
+    httpActivity.owner.addResponseCache({
+      responseCache: cacheEntry,
+    });
+  }
+
+  /**
+   * Handle the onStopRequest by closing the sink output stream.
+   *
+   * For more documentation about nsIRequestObserver go to:
+   * https://developer.mozilla.org/En/NsIRequestObserver
+   */
+  onStopRequest() {
+    // Bug 1429365: onStopRequest may be called after onComplete for resources loaded
+    // from bytecode cache.
+    if (!this.#httpActivity) {
+      return;
+    }
+    this.#sink.outputStream.close();
+  }
+
+  // nsIProgressEventSink implementation
+
+  /**
+   * Handle progress event as data is transferred.  This is used to record the
+   * size on the wire, which may be compressed / encoded.
+   */
+  onProgress(request, progress, progressMax) {
+    this.#bodySize = progress;
+
+    // Need to forward as well to keep things like Download Manager's progress
+    // bar working properly.
+    this.#forwardNotification(Ci.nsIProgressEventSink, "onProgress", arguments);
+  }
+
+  onStatus() {
+    this.#forwardNotification(Ci.nsIProgressEventSink, "onStatus", arguments);
+  }
+
+  /**
+   * Clean up the response listener once the response input stream is closed.
+   * This is called from onStopRequest() or from onInputStreamReady() when the
+   * stream is closed.
+   * @return void
+   */
+  onStreamClose() {
+    if (!this.#httpActivity) {
+      return;
+    }
+    // Remove our listener from the request input stream.
+    this.setAsyncListener(this.#sink.inputStream, null);
+
+    let responseStatus;
+    try {
+      responseStatus = this.#httpActivity.channel.responseStatus;
+    } catch (e) {
+      // Will throw NS_ERROR_NOT_AVAILABLE if the response has not been received
+      // yet.
+    }
+    if (this.#request.fromCache || responseStatus == 304) {
+      this.#fetchCacheInformation();
+    }
+
+    if (!this.#httpActivity.discardResponseBody && this.#receivedData.length) {
+      this.#onComplete(this.#receivedData);
+    } else if (
+      !this.#httpActivity.discardResponseBody &&
+      responseStatus == 304
+    ) {
+      // Response is cached, so we load it from cache.
+      let charset;
+      try {
+        charset = this.#request.contentCharset;
+      } catch (e) {
+        // Accessing the charset sometimes throws NS_ERROR_NOT_AVAILABLE when
+        // reloading the page
+      }
+      if (!charset) {
+        charset = this.#httpActivity.charset;
+      }
+      lazy.NetworkHelper.loadFromCache(
+        this.#httpActivity.url,
+        charset,
+        this.#onComplete.bind(this)
+      );
+    } else {
+      this.#onComplete();
+    }
+  }
+
+  /**
+   * Handler for when the response completes. This function cleans up the
+   * response listener.
+   *
+   * @param string [data]
+   *        Optional, the received data coming from the response listener or
+   *        from the cache.
+   */
+  #onComplete(data) {
+    // Make sure all the security and response content info are sent
+    this.#getResponseContent(data);
+    this.#onSecurityInfo.then(() => this.#destroy());
+  }
+
+  /**
+   * Create the response object and send it to the client.
+   */
+  #getResponseContent(data) {
+    const response = {
+      mimeType: "",
+      text: data || "",
+    };
+
+    response.bodySize = this.#bodySize;
+    response.decodedBodySize = this.#decodedBodySize;
+    // TODO: Stop exposing the decodedBodySize as `size` which is ambiguous.
+    // Consumers should use `decodedBodySize` instead. See Bug 1808560.
+    response.size = this.#decodedBodySize;
+    response.headersSize = this.#httpActivity.headersSize;
+    response.transferredSize = this.#bodySize + this.#httpActivity.headersSize;
+
+    try {
+      response.mimeType = this.#request.contentType;
+    } catch (ex) {
+      // Ignore.
+    }
+
+    if (
+      !response.mimeType ||
+      !lazy.NetworkHelper.isTextMimeType(response.mimeType)
+    ) {
+      response.encoding = "base64";
+      try {
+        response.text = btoa(response.text);
+      } catch (err) {
+        // Ignore.
+      }
+    }
+
+    if (response.mimeType && this.#request.contentCharset) {
+      response.mimeType += "; charset=" + this.#request.contentCharset;
+    }
+
+    this.#receivedData = "";
+
+    // Check any errors or blocking scenarios which happen late in the cycle
+    // e.g If a host is not found (NS_ERROR_UNKNOWN_HOST) or CORS blocking.
+    const { blockingExtension, blockedReason } =
+      lazy.NetworkUtils.getBlockedReason(this.#httpActivity.channel);
+
+    this.#httpActivity.owner.addResponseContent(response, {
+      discardResponseBody: this.#httpActivity.discardResponseBody,
+      truncated: this.#truncated,
+      blockedReason,
+      blockingExtension,
+    });
+  }
+
+  #destroy() {
+    this.#wrappedNotificationCallbacks = null;
+    this.#httpActivity = null;
+    this.#sink = null;
+    this.#inputStream = null;
+    this.#converter = null;
+    this.#request = null;
+
+    this.#isDestroyed = true;
+  }
+
+  /**
+   * The nsIInputStreamCallback for when the request input stream is ready -
+   * either it has more data or it is closed.
+   *
+   * @param nsIAsyncInputStream stream
+   *        The sink input stream from which data is coming.
+   * @returns void
+   */
+  onInputStreamReady(stream) {
+    if (!(stream instanceof Ci.nsIAsyncInputStream) || !this.#httpActivity) {
+      return;
+    }
+
+    let available = -1;
+    try {
+      // This may throw if the stream is closed normally or due to an error.
+      available = stream.available();
+    } catch (ex) {
+      // Ignore.
+    }
+
+    if (available != -1) {
+      if (available != 0) {
+        if (this.#converter) {
+          this.#converter.onDataAvailable(
+            this.#request,
+            stream,
+            this.#offset,
+            available
+          );
+        } else {
+          this.onDataAvailable(this.#request, stream, this.#offset, available);
+        }
+      }
+      this.#offset += available;
+      this.setAsyncListener(stream, this);
+    } else {
+      this.onStreamClose();
+      this.#offset = 0;
+    }
+  }
+
+  QueryInterface = ChromeUtils.generateQI([
+    "nsIStreamListener",
+    "nsIInputStreamCallback",
+    "nsIRequestObserver",
+    "nsIInterfaceRequestor",
+  ]);
+}
diff --git a/devtools/shared/network-observer/NetworkThrottleManager.sys.mjs b/devtools/shared/network-observer/NetworkThrottleManager.sys.mjs
new file mode 100644
index 0000000000..a643861004
--- /dev/null
+++ b/devtools/shared/network-observer/NetworkThrottleManager.sys.mjs
@@ -0,0 +1,495 @@
+/* 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/. */
+
+const ArrayBufferInputStream = Components.Constructor(
+  "@mozilla.org/io/arraybuffer-input-stream;1",
+  "nsIArrayBufferInputStream"
+);
+const BinaryInputStream = Components.Constructor(
+  "@mozilla.org/binaryinputstream;1",
+  "nsIBinaryInputStream",
+  "setInputStream"
+);
+
+import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
+
+const lazy = {};
+
+XPCOMUtils.defineLazyServiceGetter(
+  lazy,
+  "gActivityDistributor",
+  "@mozilla.org/network/http-activity-distributor;1",
+  "nsIHttpActivityDistributor"
+);
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  setTimeout: "resource://gre/modules/Timer.sys.mjs",
+});
+
+class NetworkThrottleListener {
+  #activities;
+  #offset;
+  #originalListener;
+  #pendingData;
+  #pendingException;
+  #queue;
+  #responseStarted;
+
+  /**
+   * Construct a new nsIStreamListener that buffers data and provides a
+   * method to notify another listener when data is available.  This is
+   * used to throttle network data on a per-channel basis.
+   *
+   * After construction, @see setOriginalListener must be called on the
+   * new object.
+   *
+   * @param {NetworkThrottleQueue} queue the NetworkThrottleQueue to
+   *        which status changes should be reported
+   */
+  constructor(queue) {
+    this.#activities = {};
+    this.#offset = 0;
+    this.#pendingData = [];
+    this.#pendingException = null;
+    this.#queue = queue;
+    this.#responseStarted = false;
+  }
+
+  /**
+   * Set the original listener for this object.  The original listener
+   * will receive requests from this object when the queue allows data
+   * through.
+   *
+   * @param {nsIStreamListener} originalListener the original listener
+   *        for the channel, to which all requests will be sent
+   */
+  setOriginalListener(originalListener) {
+    this.#originalListener = originalListener;
+  }
+
+  /**
+   * @see nsIStreamListener.onStartRequest.
+   */
+  onStartRequest(request) {
+    this.#originalListener.onStartRequest(request);
+    this.#queue.start(this);
+  }
+
+  /**
+   * @see nsIStreamListener.onStopRequest.
+   */
+  onStopRequest(request, statusCode) {
+    this.#pendingData.push({ request, statusCode });
+    this.#queue.dataAvailable(this);
+  }
+
+  /**
+   * @see nsIStreamListener.onDataAvailable.
+   */
+  onDataAvailable(request, inputStream, offset, count) {
+    if (this.#pendingException) {
+      throw this.#pendingException;
+    }
+
+    const bin = new BinaryInputStream(inputStream);
+    const bytes = new ArrayBuffer(count);
+    bin.readArrayBuffer(count, bytes);
+
+    const stream = new ArrayBufferInputStream();
+    stream.setData(bytes, 0, count);
+
+    this.#pendingData.push({ request, stream, count });
+    this.#queue.dataAvailable(this);
+  }
+
+  /**
+   * Allow some buffered data from this object to be forwarded to this
+   * object's originalListener.
+   *
+   * @param {Number} bytesPermitted The maximum number of bytes
+   *        permitted to be sent.
+   * @return {Object} an object of the form {length, done}, where
+   *         |length| is the number of bytes actually forwarded, and
+   *         |done| is a boolean indicating whether this particular
+   *         request has been completed.  (A NetworkThrottleListener
+   *         may be queued multiple times, so this does not mean that
+   *         all available data has been sent.)
+   */
+  sendSomeData(bytesPermitted) {
+    if (this.#pendingData.length === 0) {
+      // Shouldn't happen.
+      return { length: 0, done: true };
+    }
+
+    const { request, stream, count, statusCode } = this.#pendingData[0];
+
+    if (statusCode !== undefined) {
+      this.#pendingData.shift();
+      this.#originalListener.onStopRequest(request, statusCode);
+      return { length: 0, done: true };
+    }
+
+    if (bytesPermitted > count) {
+      bytesPermitted = count;
+    }
+
+    try {
+      this.#originalListener.onDataAvailable(
+        request,
+        stream,
+        this.#offset,
+        bytesPermitted
+      );
+    } catch (e) {
+      this.#pendingException = e;
+    }
+
+    let done = false;
+    if (bytesPermitted === count) {
+      this.#pendingData.shift();
+      done = true;
+    } else {
+      this.#pendingData[0].count -= bytesPermitted;
+    }
+
+    this.#offset += bytesPermitted;
+    // Maybe our state has changed enough to emit an event.
+    this.#maybeEmitEvents();
+
+    return { length: bytesPermitted, done };
+  }
+
+  /**
+   * Return the number of pending data requests available for this
+   * listener.
+   */
+  pendingCount() {
+    return this.#pendingData.length;
+  }
+
+  /**
+   * This is called when an http activity event is delivered.  This
+   * object delays the event until the appropriate moment.
+   */
+  addActivityCallback(
+    callback,
+    httpActivity,
+    channel,
+    activityType,
+    activitySubtype,
+    timestamp,
+    extraSizeData,
+    extraStringData
+  ) {
+    const datum = {
+      callback,
+      httpActivity,
+      channel,
+      activityType,
+      activitySubtype,
+      extraSizeData,
+      extraStringData,
+    };
+    this.#activities[activitySubtype] = datum;
+
+    if (
+      activitySubtype ===
+      lazy.gActivityDistributor.ACTIVITY_SUBTYPE_RESPONSE_COMPLETE
+    ) {
+      this.totalSize = extraSizeData;
+    }
+
+    this.#maybeEmitEvents();
+  }
+
+  /**
+   * This is called for a download throttler when the latency timeout
+   * has ended.
+   */
+  responseStart() {
+    this.#responseStarted = true;
+    this.#maybeEmitEvents();
+  }
+
+  /**
+   * Check our internal state and emit any http activity events as
+   * needed.  Note that we wait until both our internal state has
+   * changed and we've received the real http activity event from
+   * platform.  This approach ensures we can both pass on the correct
+   * data from the original event, and update the reported time to be
+   * consistent with the delay we're introducing.
+   */
+  #maybeEmitEvents() {
+    if (this.#responseStarted) {
+      this.#maybeEmit(
+        lazy.gActivityDistributor.ACTIVITY_SUBTYPE_RESPONSE_START
+      );
+      this.#maybeEmit(
+        lazy.gActivityDistributor.ACTIVITY_SUBTYPE_RESPONSE_HEADER
+      );
+    }
+
+    if (this.totalSize !== undefined && this.#offset >= this.totalSize) {
+      this.#maybeEmit(
+        lazy.gActivityDistributor.ACTIVITY_SUBTYPE_RESPONSE_COMPLETE
+      );
+      this.#maybeEmit(
+        lazy.gActivityDistributor.ACTIVITY_SUBTYPE_TRANSACTION_CLOSE
+      );
+    }
+  }
+
+  /**
+   * Emit an event for |code|, if the appropriate entry in
+   * |activities| is defined.
+   */
+  #maybeEmit(code) {
+    if (this.#activities[code] !== undefined) {
+      const {
+        callback,
+        httpActivity,
+        channel,
+        activityType,
+        activitySubtype,
+        extraSizeData,
+        extraStringData,
+      } = this.#activities[code];
+      const now = Date.now() * 1000;
+      callback(
+        httpActivity,
+        channel,
+        activityType,
+        activitySubtype,
+        now,
+        extraSizeData,
+        extraStringData
+      );
+      this.#activities[code] = undefined;
+    }
+  }
+
+  QueryInterface = ChromeUtils.generateQI([
+    "nsIStreamListener",
+    "nsIInterfaceRequestor",
+  ]);
+}
+
+class NetworkThrottleQueue {
+  #downloadQueue;
+  #latencyMax;
+  #latencyMean;
+  #maxBPS;
+  #meanBPS;
+  #pendingRequests;
+  #previousReads;
+  #pumping;
+
+  /**
+   * Construct a new queue that can be used to throttle the network for
+   * a group of related network requests.
+   *
+   * meanBPS {Number} Mean bytes per second.
+   * maxBPS {Number} Maximum bytes per second.
+   * latencyMean {Number} Mean latency in milliseconds.
+   * latencyMax {Number} Maximum latency in milliseconds.
+   */
+  constructor(meanBPS, maxBPS, latencyMean, latencyMax) {
+    this.#meanBPS = meanBPS;
+    this.#maxBPS = maxBPS;
+    this.#latencyMean = latencyMean;
+    this.#latencyMax = latencyMax;
+
+    this.#pendingRequests = new Set();
+    this.#downloadQueue = [];
+    this.#previousReads = [];
+
+    this.#pumping = false;
+  }
+
+  /**
+   * A helper function that lets the indicating listener start sending
+   * data.  This is called after the initial round trip time for the
+   * listener has elapsed.
+   */
+  #allowDataFrom(throttleListener) {
+    throttleListener.responseStart();
+    this.#pendingRequests.delete(throttleListener);
+    const count = throttleListener.pendingCount();
+    for (let i = 0; i < count; ++i) {
+      this.#downloadQueue.push(throttleListener);
+    }
+    this.#pump();
+  }
+
+  /**
+   * An internal function that permits individual listeners to send
+   * data.
+   */
+  #pump() {
+    // A redirect will cause two NetworkThrottleListeners to be on a
+    // listener chain.  In this case, we might recursively call into
+    // this method.  Avoid infinite recursion here.
+    if (this.#pumping) {
+      return;
+    }
+    this.#pumping = true;
+
+    const now = Date.now();
+    const oneSecondAgo = now - 1000;
+
+    while (
+      this.#previousReads.length &&
+      this.#previousReads[0].when < oneSecondAgo
+    ) {
+      this.#previousReads.shift();
+    }
+
+    const totalBytes = this.#previousReads.reduce((sum, elt) => {
+      return sum + elt.numBytes;
+    }, 0);
+
+    let thisSliceBytes = this.#random(this.#meanBPS, this.#maxBPS);
+    if (totalBytes < thisSliceBytes) {
+      thisSliceBytes -= totalBytes;
+      let readThisTime = 0;
+      while (thisSliceBytes > 0 && this.#downloadQueue.length) {
+        const { length, done } =
+          this.#downloadQueue[0].sendSomeData(thisSliceBytes);
+        thisSliceBytes -= length;
+        readThisTime += length;
+        if (done) {
+          this.#downloadQueue.shift();
+        }
+      }
+      this.#previousReads.push({ when: now, numBytes: readThisTime });
+    }
+
+    // If there is more data to download, then schedule ourselves for
+    // one second after the oldest previous read.
+    if (this.#downloadQueue.length) {
+      const when = this.#previousReads[0].when + 1000;
+      lazy.setTimeout(this.#pump.bind(this), when - now);
+    }
+
+    this.#pumping = false;
+  }
+
+  /**
+   * A helper function that, given a mean and a maximum, returns a
+   * random integer between (mean - (max - mean)) and max.
+   */
+  #random(mean, max) {
+    return mean - (max - mean) + Math.floor(2 * (max - mean) * Math.random());
+  }
+
+  /**
+   * Notice a new listener object.  This is called by the
+   * NetworkThrottleListener when the request has started.  Initially
+   * a new listener object is put into a "pending" state, until the
+   * round-trip time has elapsed.  This is used to simulate latency.
+   *
+   * @param {NetworkThrottleListener} throttleListener the new listener
+   */
+  start(throttleListener) {
+    this.#pendingRequests.add(throttleListener);
+    const delay = this.#random(this.#latencyMean, this.#latencyMax);
+    if (delay > 0) {
+      lazy.setTimeout(() => this.#allowDataFrom(throttleListener), delay);
+    } else {
+      this.#allowDataFrom(throttleListener);
+    }
+  }
+
+  /**
+   * Note that new data is available for a given listener.  Each time
+   * data is available, the listener will be re-queued.
+   *
+   * @param {NetworkThrottleListener} throttleListener the listener
+   *        which has data available.
+   */
+  dataAvailable(throttleListener) {
+    if (!this.#pendingRequests.has(throttleListener)) {
+      this.#downloadQueue.push(throttleListener);
+      this.#pump();
+    }
+  }
+}
+
+/**
+ * Construct a new object that can be used to throttle the network for
+ * a group of related network requests.
+ *
+ * @param {Object} An object with the following attributes:
+ * latencyMean {Number} Mean latency in milliseconds.
+ * latencyMax {Number} Maximum latency in milliseconds.
+ * downloadBPSMean {Number} Mean bytes per second for downloads.
+ * downloadBPSMax {Number} Maximum bytes per second for downloads.
+ * uploadBPSMean {Number} Mean bytes per second for uploads.
+ * uploadBPSMax {Number} Maximum bytes per second for uploads.
+ *
+ * Download throttling will not be done if downloadBPSMean and
+ * downloadBPSMax are <= 0.  Upload throttling will not be done if
+ * uploadBPSMean and uploadBPSMax are <= 0.
+ */
+export class NetworkThrottleManager {
+  #downloadQueue;
+
+  constructor({
+    latencyMean,
+    latencyMax,
+    downloadBPSMean,
+    downloadBPSMax,
+    uploadBPSMean,
+    uploadBPSMax,
+  }) {
+    if (downloadBPSMax <= 0 && downloadBPSMean <= 0) {
+      this.#downloadQueue = null;
+    } else {
+      this.#downloadQueue = new NetworkThrottleQueue(
+        downloadBPSMean,
+        downloadBPSMax,
+        latencyMean,
+        latencyMax
+      );
+    }
+    if (uploadBPSMax <= 0 && uploadBPSMean <= 0) {
+      this.uploadQueue = null;
+    } else {
+      this.uploadQueue = Cc[
+        "@mozilla.org/network/throttlequeue;1"
+      ].createInstance(Ci.nsIInputChannelThrottleQueue);
+      this.uploadQueue.init(uploadBPSMean, uploadBPSMax);
+    }
+  }
+
+  /**
+   * Create a new NetworkThrottleListener for a given channel and
+   * install it using |setNewListener|.
+   *
+   * @param {nsITraceableChannel} channel the channel to manage
+   * @return {NetworkThrottleListener} the new listener, or null if
+   *         download throttling is not being done.
+   */
+  manage(channel) {
+    if (this.#downloadQueue) {
+      const listener = new NetworkThrottleListener(this.#downloadQueue);
+      const originalListener = channel.setNewListener(listener);
+      listener.setOriginalListener(originalListener);
+      return listener;
+    }
+    return null;
+  }
+
+  /**
+   * Throttle uploads taking place on the given channel.
+   *
+   * @param {nsITraceableChannel} channel the channel to manage
+   */
+  manageUpload(channel) {
+    if (this.uploadQueue) {
+      channel = channel.QueryInterface(Ci.nsIThrottledInputChannel);
+      channel.throttleQueue = this.uploadQueue;
+    }
+  }
+}
diff --git a/devtools/shared/network-observer/NetworkUtils.sys.mjs b/devtools/shared/network-observer/NetworkUtils.sys.mjs
new file mode 100644
index 0000000000..44de9fa353
--- /dev/null
+++ b/devtools/shared/network-observer/NetworkUtils.sys.mjs
@@ -0,0 +1,670 @@
+/* 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/. */
+
+import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  NetworkHelper:
+    "resource://devtools/shared/network-observer/NetworkHelper.sys.mjs",
+});
+
+XPCOMUtils.defineLazyGetter(lazy, "tpFlagsMask", () => {
+  const trackingProtectionLevel2Enabled = Services.prefs
+    .getStringPref("urlclassifier.trackingTable")
+    .includes("content-track-digest256");
+
+  return trackingProtectionLevel2Enabled
+    ? ~Ci.nsIClassifiedChannel.CLASSIFIED_ANY_BASIC_TRACKING &
+        ~Ci.nsIClassifiedChannel.CLASSIFIED_ANY_STRICT_TRACKING
+    : ~Ci.nsIClassifiedChannel.CLASSIFIED_ANY_BASIC_TRACKING &
+        Ci.nsIClassifiedChannel.CLASSIFIED_ANY_STRICT_TRACKING;
+});
+
+/**
+ * Convert a nsIContentPolicy constant to a display string
+ */
+const LOAD_CAUSE_STRINGS = {
+  [Ci.nsIContentPolicy.TYPE_INVALID]: "invalid",
+  [Ci.nsIContentPolicy.TYPE_OTHER]: "other",
+  [Ci.nsIContentPolicy.TYPE_SCRIPT]: "script",
+  [Ci.nsIContentPolicy.TYPE_IMAGE]: "img",
+  [Ci.nsIContentPolicy.TYPE_STYLESHEET]: "stylesheet",
+  [Ci.nsIContentPolicy.TYPE_OBJECT]: "object",
+  [Ci.nsIContentPolicy.TYPE_DOCUMENT]: "document",
+  [Ci.nsIContentPolicy.TYPE_SUBDOCUMENT]: "subdocument",
+  [Ci.nsIContentPolicy.TYPE_PING]: "ping",
+  [Ci.nsIContentPolicy.TYPE_XMLHTTPREQUEST]: "xhr",
+  [Ci.nsIContentPolicy.TYPE_OBJECT_SUBREQUEST]: "objectSubdoc",
+  [Ci.nsIContentPolicy.TYPE_DTD]: "dtd",
+  [Ci.nsIContentPolicy.TYPE_FONT]: "font",
+  [Ci.nsIContentPolicy.TYPE_MEDIA]: "media",
+  [Ci.nsIContentPolicy.TYPE_WEBSOCKET]: "websocket",
+  [Ci.nsIContentPolicy.TYPE_CSP_REPORT]: "csp",
+  [Ci.nsIContentPolicy.TYPE_XSLT]: "xslt",
+  [Ci.nsIContentPolicy.TYPE_BEACON]: "beacon",
+  [Ci.nsIContentPolicy.TYPE_FETCH]: "fetch",
+  [Ci.nsIContentPolicy.TYPE_IMAGESET]: "imageset",
+  [Ci.nsIContentPolicy.TYPE_WEB_MANIFEST]: "webManifest",
+  [Ci.nsIContentPolicy.TYPE_WEB_IDENTITY]: "webidentity",
+};
+
+function causeTypeToString(causeType, loadFlags, internalContentPolicyType) {
+  let prefix = "";
+  if (
+    (causeType == Ci.nsIContentPolicy.TYPE_IMAGESET ||
+      internalContentPolicyType == Ci.nsIContentPolicy.TYPE_INTERNAL_IMAGE) &&
+    loadFlags & Ci.nsIRequest.LOAD_BACKGROUND
+  ) {
+    prefix = "lazy-";
+  }
+
+  return prefix + LOAD_CAUSE_STRINGS[causeType] || "unknown";
+}
+
+function stringToCauseType(value) {
+  return Object.keys(LOAD_CAUSE_STRINGS).find(
+    key => LOAD_CAUSE_STRINGS[key] === value
+  );
+}
+
+function isChannelFromSystemPrincipal(channel) {
+  let principal = null;
+  let browsingContext = channel.loadInfo.browsingContext;
+  if (!browsingContext) {
+    const topFrame = lazy.NetworkHelper.getTopFrameForRequest(channel);
+    if (topFrame) {
+      browsingContext = topFrame.browsingContext;
+    } else {
+      // Fallback to the triggering principal when browsingContext and topFrame is null
+      // e.g some chrome requests
+      principal = channel.loadInfo.triggeringPrincipal;
+    }
+  }
+
+  // When in the parent process, we can get the documentPrincipal from the
+  // WindowGlobal which is available on the BrowsingContext
+  if (!principal) {
+    principal = CanonicalBrowsingContext.isInstance(browsingContext)
+      ? browsingContext.currentWindowGlobal.documentPrincipal
+      : browsingContext.window.document.nodePrincipal;
+  }
+  return principal.isSystemPrincipal;
+}
+
+/**
+ * Get the browsing context id for the channel.
+ *
+ * @param {*} channel
+ * @returns {number}
+ */
+function getChannelBrowsingContextID(channel) {
+  if (channel.loadInfo.browsingContextID) {
+    return channel.loadInfo.browsingContextID;
+  }
+  // At least WebSocket channel aren't having a browsingContextID set on their loadInfo
+  // We fallback on top frame element, which works, but will be wrong for WebSocket
+  // in same-process iframes...
+  const topFrame = lazy.NetworkHelper.getTopFrameForRequest(channel);
+  // topFrame is typically null for some chrome requests like favicons
+  if (topFrame && topFrame.browsingContext) {
+    return topFrame.browsingContext.id;
+  }
+  return null;
+}
+
+/**
+ * Get the innerWindowId for the channel.
+ *
+ * @param {*} channel
+ * @returns {number}
+ */
+function getChannelInnerWindowId(channel) {
+  if (channel.loadInfo.innerWindowID) {
+    return channel.loadInfo.innerWindowID;
+  }
+  // At least WebSocket channel aren't having a browsingContextID set on their loadInfo
+  // We fallback on top frame element, which works, but will be wrong for WebSocket
+  // in same-process iframes...
+  const topFrame = lazy.NetworkHelper.getTopFrameForRequest(channel);
+  // topFrame is typically null for some chrome requests like favicons
+  if (topFrame?.browsingContext?.currentWindowGlobal) {
+    return topFrame.browsingContext.currentWindowGlobal.innerWindowId;
+  }
+  return null;
+}
+
+/**
+ * Does this channel represent a Preload request.
+ *
+ * @param {*} channel
+ * @returns {boolean}
+ */
+function isPreloadRequest(channel) {
+  const type = channel.loadInfo.internalContentPolicyType;
+  return (
+    type == Ci.nsIContentPolicy.TYPE_INTERNAL_SCRIPT_PRELOAD ||
+    type == Ci.nsIContentPolicy.TYPE_INTERNAL_MODULE_PRELOAD ||
+    type == Ci.nsIContentPolicy.TYPE_INTERNAL_IMAGE_PRELOAD ||
+    type == Ci.nsIContentPolicy.TYPE_INTERNAL_STYLESHEET_PRELOAD ||
+    type == Ci.nsIContentPolicy.TYPE_INTERNAL_FONT_PRELOAD
+  );
+}
+
+/**
+ * Get the channel cause details.
+ *
+ * @param {nsIChannel} channel
+ * @returns {Object}
+ *          - loadingDocumentUri {string} uri of the document which created the
+ *            channel
+ *          - type {string} cause type as string
+ */
+function getCauseDetails(channel) {
+  // Determine the cause and if this is an XHR request.
+  let causeType = Ci.nsIContentPolicy.TYPE_OTHER;
+  let causeUri = null;
+
+  if (channel.loadInfo) {
+    causeType = channel.loadInfo.externalContentPolicyType;
+    const { loadingPrincipal } = channel.loadInfo;
+    if (loadingPrincipal) {
+      causeUri = loadingPrincipal.spec;
+    }
+  }
+
+  return {
+    loadingDocumentUri: causeUri,
+    type: causeTypeToString(
+      causeType,
+      channel.loadFlags,
+      channel.loadInfo.internalContentPolicyType
+    ),
+  };
+}
+
+/**
+ * Get the channel priority. Priority is a number which typically ranges from
+ * -20 (lowest priority) to 20 (highest priority). Can be null if the channel
+ * does not implement nsISupportsPriority.
+ *
+ * @param {nsIChannel} channel
+ * @returns {number|undefined}
+ */
+function getChannelPriority(channel) {
+  if (channel instanceof Ci.nsISupportsPriority) {
+    return channel.priority;
+  }
+
+  return null;
+}
+
+/**
+ * Get the channel HTTP version as an uppercase string starting with "HTTP/"
+ * (eg "HTTP/2").
+ *
+ * @param {nsIChannel} channel
+ * @returns {string}
+ */
+function getHttpVersion(channel) {
+  // Determine the HTTP version.
+  const httpVersionMaj = {};
+  const httpVersionMin = {};
+
+  channel.QueryInterface(Ci.nsIHttpChannelInternal);
+  channel.getResponseVersion(httpVersionMaj, httpVersionMin);
+
+  // The official name HTTP version 2.0 and 3.0 are HTTP/2 and HTTP/3, omit the
+  // trailing `.0`.
+  if (httpVersionMin.value == 0) {
+    return "HTTP/" + httpVersionMaj.value;
+  }
+
+  return "HTTP/" + httpVersionMaj.value + "." + httpVersionMin.value;
+}
+
+const UNKNOWN_PROTOCOL_STRINGS = ["", "unknown"];
+const HTTP_PROTOCOL_STRINGS = ["http", "https"];
+/**
+ * Get the protocol for the provided httpActivity. Either the ALPN negotiated
+ * protocol or as a fallback a protocol computed from the scheme and the
+ * response status.
+ *
+ * TODO: The `protocol` is similar to another response property called
+ * `httpVersion`. `httpVersion` is uppercase and purely computed from the
+ * response status, whereas `protocol` uses nsIHttpChannel.protocolVersion by
+ * default and otherwise falls back on `httpVersion`. Ideally we should merge
+ * the two properties.
+ *
+ * @param {Object} httpActivity
+ *     The httpActivity object for which we need to get the protocol.
+ *
+ * @returns {string}
+ *     The protocol as a string.
+ */
+function getProtocol(channel) {
+  let protocol = "";
+  try {
+    const httpChannel = channel.QueryInterface(Ci.nsIHttpChannel);
+    // protocolVersion corresponds to ALPN negotiated protocol.
+    protocol = httpChannel.protocolVersion;
+  } catch (e) {
+    // Ignore errors reading protocolVersion.
+  }
+
+  if (UNKNOWN_PROTOCOL_STRINGS.includes(protocol)) {
+    protocol = channel.URI.scheme;
+    const httpVersion = getHttpVersion(channel);
+    if (
+      typeof httpVersion == "string" &&
+      HTTP_PROTOCOL_STRINGS.includes(protocol)
+    ) {
+      protocol = httpVersion.toLowerCase();
+    }
+  }
+
+  return protocol;
+}
+
+/**
+ * Get the channel referrer policy as a string
+ * (eg "strict-origin-when-cross-origin").
+ *
+ * @param {nsIChannel} channel
+ * @returns {string}
+ */
+function getReferrerPolicy(channel) {
+  return channel.referrerInfo
+    ? channel.referrerInfo.getReferrerPolicyString()
+    : "";
+}
+
+/**
+ * Check if the channel is private.
+ *
+ * @param {nsIChannel} channel
+ * @returns {boolean}
+ */
+function isChannelPrivate(channel) {
+  channel.QueryInterface(Ci.nsIPrivateBrowsingChannel);
+  return channel.isChannelPrivate;
+}
+
+/**
+ * Check if the channel data is loaded from the cache or not.
+ *
+ * @param {nsIChannel} channel
+ *     The channel for which we need to check the cache status.
+ *
+ * @returns {boolean}
+ *     True if the channel data is loaded from the cache, false otherwise.
+ */
+function isFromCache(channel) {
+  if (channel instanceof Ci.nsICacheInfoChannel) {
+    return channel.isFromCache();
+  }
+
+  return false;
+}
+
+const REDIRECT_STATES = [
+  301, // HTTP Moved Permanently
+  302, // HTTP Found
+  303, // HTTP See Other
+  307, // HTTP Temporary Redirect
+];
+/**
+ * Check if the channel's status corresponds to a known redirect status.
+ *
+ * @param {nsIChannel} channel
+ *     The channel for which we need to check the redirect status.
+ *
+ * @returns {boolean}
+ *     True if the channel data is a redirect, false otherwise.
+ */
+function isRedirectedChannel(channel) {
+  try {
+    return REDIRECT_STATES.includes(channel.responseStatus);
+  } catch (e) {
+    // Throws NS_ERROR_NOT_AVAILABLE if the request was not sent yet.
+  }
+  return false;
+}
+
+/**
+ * isNavigationRequest is true for the one request used to load a new top level
+ * document of a given tab, or top level window. It will typically be false for
+ * navigation requests of iframes, i.e. the request loading another document in
+ * an iframe.
+ *
+ * @param {nsIChannel} channel
+ * @return {boolean}
+ */
+function isNavigationRequest(channel) {
+  return channel.isMainDocumentChannel && channel.loadInfo.isTopLevelLoad;
+}
+
+/**
+ * Returns true  if the channel has been processed by URL-Classifier features
+ * and is considered third-party with the top window URI, and if it has loaded
+ * a resource that is classified as a tracker.
+ *
+ * @param {nsIChannel} channel
+ * @return {boolean}
+ */
+function isThirdPartyTrackingResource(channel) {
+  // Only consider channels classified as level-1 to be trackers if our preferences
+  // would not cause such channels to be blocked in strict content blocking mode.
+  // Make sure the value produced here is a boolean.
+  return !!(
+    channel instanceof Ci.nsIClassifiedChannel &&
+    channel.isThirdPartyTrackingResource() &&
+    (channel.thirdPartyClassificationFlags & lazy.tpFlagsMask) == 0
+  );
+}
+
+/**
+ * Retrieve the websocket channel for the provided channel, if available.
+ * Returns null otherwise.
+ *
+ * @param {nsIChannel} channel
+ * @returns {nsIWebSocketChannel|null}
+ */
+function getWebSocketChannel(channel) {
+  let wsChannel = null;
+  if (channel.notificationCallbacks) {
+    try {
+      wsChannel = channel.notificationCallbacks.QueryInterface(
+        Ci.nsIWebSocketChannel
+      );
+    } catch (e) {
+      // Not all channels implement nsIWebSocketChannel.
+    }
+  }
+  return wsChannel;
+}
+
+/**
+ * For a given channel, fetch the request's headers and cookies.
+ *
+ * @param {nsIChannel} channel
+ * @return {Object}
+ *     An object with two properties:
+ *     @property {Array<Object>} cookies
+ *         Array of { name, value } objects.
+ *     @property {Array<Object>} headers
+ *         Array of { name, value } objects.
+ */
+function fetchRequestHeadersAndCookies(channel) {
+  const headers = [];
+  let cookies = [];
+  let cookieHeader = null;
+
+  // Copy the request header data.
+  channel.visitRequestHeaders({
+    visitHeader(name, value) {
+      if (name == "Cookie") {
+        cookieHeader = value;
+      }
+      headers.push({ name, value });
+    },
+  });
+
+  if (cookieHeader) {
+    cookies = lazy.NetworkHelper.parseCookieHeader(cookieHeader);
+  }
+
+  return { cookies, headers };
+}
+
+/**
+ * For a given channel, fetch the response's headers and cookies.
+ *
+ * @param {nsIChannel} channel
+ * @return {Object}
+ *     An object with two properties:
+ *     @property {Array<Object>} cookies
+ *         Array of { name, value } objects.
+ *     @property {Array<Object>} headers
+ *         Array of { name, value } objects.
+ */
+function fetchResponseHeadersAndCookies(channel) {
+  // Read response headers and cookies.
+  const headers = [];
+  const setCookieHeaders = [];
+
+  const SET_COOKIE_REGEXP = /set-cookie/i;
+  channel.visitOriginalResponseHeaders({
+    visitHeader(name, value) {
+      if (SET_COOKIE_REGEXP.test(name)) {
+        setCookieHeaders.push(value);
+      }
+      headers.push({ name, value });
+    },
+  });
+
+  return {
+    cookies: lazy.NetworkHelper.parseSetCookieHeaders(setCookieHeaders),
+    headers,
+  };
+}
+
+/**
+ * Check if a given network request should be logged by a network monitor
+ * based on the specified filters.
+ *
+ * @param nsIHttpChannel channel
+ *        Request to check.
+ * @param filters
+ *        NetworkObserver filters to match against. An object with one of the following attributes:
+ *        - sessionContext: When inspecting requests from the parent process, pass the WatcherActor's session context.
+ *          This helps know what is the overall debugged scope.
+ *          See watcher actor constructor for more info.
+ *        - targetActor: When inspecting requests from the content process, pass the WindowGlobalTargetActor.
+ *          This helps know what exact subset of request we should accept.
+ *          This is especially useful to behave correctly regarding EFT, where we should include or not
+ *          iframes requests.
+ *        - browserId, addonId, window: All these attributes are legacy.
+ *          Only browserId attribute is still used by the legacy WebConsoleActor startListener API.
+ * @return boolean
+ *         True if the network request should be logged, false otherwise.
+ */
+function matchRequest(channel, filters) {
+  // NetworkEventWatcher should now pass a session context for the parent process codepath
+  if (filters.sessionContext) {
+    const { type } = filters.sessionContext;
+    if (type == "all") {
+      return true;
+    }
+
+    // Ignore requests from chrome or add-on code when we don't monitor the whole browser
+    if (
+      channel.loadInfo?.loadingDocument === null &&
+      (channel.loadInfo.loadingPrincipal ===
+        Services.scriptSecurityManager.getSystemPrincipal() ||
+        channel.loadInfo.isInDevToolsContext)
+    ) {
+      return false;
+    }
+
+    if (type == "browser-element") {
+      if (!channel.loadInfo.browsingContext) {
+        const topFrame = lazy.NetworkHelper.getTopFrameForRequest(channel);
+        // `topFrame` is typically null for some chrome requests like favicons
+        // And its `browsingContext` attribute might be null if the request happened
+        // while the tab is being closed.
+        return (
+          topFrame?.browsingContext?.browserId ==
+          filters.sessionContext.browserId
+        );
+      }
+      return (
+        channel.loadInfo.browsingContext.browserId ==
+        filters.sessionContext.browserId
+      );
+    }
+    if (type == "webextension") {
+      return (
+        channel.loadInfo?.loadingPrincipal?.addonId ===
+        filters.sessionContext.addonId
+      );
+    }
+    throw new Error("Unsupported session context type: " + type);
+  }
+
+  // NetworkEventContentWatcher and NetworkEventStackTraces pass a target actor instead, from the content processes
+  // Because of EFT, we can't use session context as we have to know what exact windows the target actor covers.
+  if (filters.targetActor) {
+    // Bug 1769982 the target actor might be destroying and accessing windows will throw.
+    // Ignore all further request when this happens.
+    let windows;
+    try {
+      windows = filters.targetActor.windows;
+    } catch (e) {
+      return false;
+    }
+    const win = lazy.NetworkHelper.getWindowForRequest(channel);
+    return windows.includes(win);
+  }
+
+  // This is fallback code for the legacy WebConsole.startListeners codepath,
+  // which may still pass individual browserId/window/addonId attributes.
+  // This should be removable once we drop the WebConsole codepath for network events
+  // (bug 1721592 and followups)
+  return legacyMatchRequest(channel, filters);
+}
+
+function legacyMatchRequest(channel, filters) {
+  // Log everything if no filter is specified
+  if (!filters.browserId && !filters.window && !filters.addonId) {
+    return true;
+  }
+
+  // Ignore requests from chrome or add-on code when we are monitoring
+  // content.
+  if (
+    channel.loadInfo?.loadingDocument === null &&
+    (channel.loadInfo.loadingPrincipal ===
+      Services.scriptSecurityManager.getSystemPrincipal() ||
+      channel.loadInfo.isInDevToolsContext)
+  ) {
+    return false;
+  }
+
+  if (filters.window) {
+    let win = lazy.NetworkHelper.getWindowForRequest(channel);
+    if (filters.matchExactWindow) {
+      return win == filters.window;
+    }
+
+    // Since frames support, this.window may not be the top level content
+    // frame, so that we can't only compare with win.top.
+    while (win) {
+      if (win == filters.window) {
+        return true;
+      }
+      if (win.parent == win) {
+        break;
+      }
+      win = win.parent;
+    }
+    return false;
+  }
+
+  if (filters.browserId) {
+    const topFrame = lazy.NetworkHelper.getTopFrameForRequest(channel);
+    // `topFrame` is typically null for some chrome requests like favicons
+    // And its `browsingContext` attribute might be null if the request happened
+    // while the tab is being closed.
+    if (topFrame?.browsingContext?.browserId == filters.browserId) {
+      return true;
+    }
+
+    // If we couldn't get the top frame BrowsingContext from the loadContext,
+    // look for it on channel.loadInfo instead.
+    if (channel.loadInfo?.browsingContext?.browserId == filters.browserId) {
+      return true;
+    }
+  }
+
+  if (
+    filters.addonId &&
+    channel.loadInfo?.loadingPrincipal?.addonId === filters.addonId
+  ) {
+    return true;
+  }
+
+  return false;
+}
+
+function getBlockedReason(channel) {
+  let blockingExtension, blockedReason;
+  const { status } = channel;
+
+  try {
+    const request = channel.QueryInterface(Ci.nsIHttpChannel);
+    const properties = request.QueryInterface(Ci.nsIPropertyBag);
+
+    blockedReason = request.loadInfo.requestBlockingReason;
+    blockingExtension = properties.getProperty("cancelledByExtension");
+
+    // WebExtensionPolicy is not available for workers
+    if (typeof WebExtensionPolicy !== "undefined") {
+      blockingExtension = WebExtensionPolicy.getByID(blockingExtension).name;
+    }
+  } catch (err) {
+    // "cancelledByExtension" doesn't have to be available.
+  }
+  // These are platform errors which are not exposed to the users,
+  // usually the requests (with these errors) might be displayed with various
+  // other status codes.
+  const ignoreList = [
+    // This is emited when the request is already in the cache.
+    "NS_ERROR_PARSED_DATA_CACHED",
+    // This is emited when there is some issues around images e.g When the img.src
+    // links to a non existent url. This is typically shown as a 404 request.
+    "NS_IMAGELIB_ERROR_FAILURE",
+    // This is emited when there is a redirect. They are shown as 301 requests.
+    "NS_BINDING_REDIRECTED",
+    // E.g Emited by send beacon requests.
+    "NS_ERROR_ABORT",
+  ];
+
+  // If the request has not failed or is not blocked by a web extension, check for
+  // any errors not on the ignore list. e.g When a host is not found (NS_ERROR_UNKNOWN_HOST).
+  if (
+    blockedReason == 0 &&
+    !Components.isSuccessCode(status) &&
+    !ignoreList.includes(ChromeUtils.getXPCOMErrorName(status))
+  ) {
+    blockedReason = ChromeUtils.getXPCOMErrorName(status);
+  }
+
+  return { blockingExtension, blockedReason };
+}
+
+export const NetworkUtils = {
+  causeTypeToString,
+  fetchRequestHeadersAndCookies,
+  fetchResponseHeadersAndCookies,
+  getCauseDetails,
+  getChannelBrowsingContextID,
+  getChannelInnerWindowId,
+  getChannelPriority,
+  getHttpVersion,
+  getProtocol,
+  getReferrerPolicy,
+  getWebSocketChannel,
+  isChannelFromSystemPrincipal,
+  isChannelPrivate,
+  isFromCache,
+  isNavigationRequest,
+  isPreloadRequest,
+  isRedirectedChannel,
+  isThirdPartyTrackingResource,
+  matchRequest,
+  stringToCauseType,
+  getBlockedReason,
+};
diff --git a/devtools/shared/network-observer/README.md b/devtools/shared/network-observer/README.md
new file mode 100644
index 0000000000..7c2d41a959
--- /dev/null
+++ b/devtools/shared/network-observer/README.md
@@ -0,0 +1,9 @@
+# Network Observer modules
+
+The NetworkObserver module and associated helpers allow to:
+- monitor network events (requests and responses)
+- block requests
+- throttle responses
+
+The DevTools network-observer modules are used both by DevTools and by WebDriver BiDi, found under /remote.
+Breaking changes should be discussed and reviewed both by devtools and webdriver peers.
diff --git a/devtools/shared/network-observer/WildcardToRegexp.sys.mjs b/devtools/shared/network-observer/WildcardToRegexp.sys.mjs
new file mode 100644
index 0000000000..4c495fdd78
--- /dev/null
+++ b/devtools/shared/network-observer/WildcardToRegexp.sys.mjs
@@ -0,0 +1,28 @@
+/* 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/. */
+
+/**
+ * Converts a URL-like string which might include the `*` character as a wildcard
+ * to a regular expression. They are used to match against actual URLs for the
+ * request blocking feature from DevTools.
+ *
+ * The returned regular expression is case insensitive.
+ *
+ * @param {string} url
+ *     A URL-like string which can contain one or several `*` as wildcard
+ *     characters.
+ * @return {RegExp}
+ *     A regular expression which can be used to match URLs compatible with the
+ *     provided url "template".
+ */
+export function wildcardToRegExp(url) {
+  return new RegExp(url.split("*").map(regExpEscape).join(".*"), "i");
+}
+
+/**
+ * Escapes all special RegExp characters in the given string.
+ */
+const regExpEscape = s => {
+  return s.replace(/[|\\{}()[\]^$+*?.]/g, "\\$&");
+};
diff --git a/devtools/shared/network-observer/moz.build b/devtools/shared/network-observer/moz.build
new file mode 100644
index 0000000000..71ba8bf3db
--- /dev/null
+++ b/devtools/shared/network-observer/moz.build
@@ -0,0 +1,20 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# 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/.
+
+BROWSER_CHROME_MANIFESTS += ["test/browser/browser.ini"]
+
+XPCSHELL_TESTS_MANIFESTS += ["test/xpcshell/xpcshell.ini"]
+
+DevToolsModules(
+    "ChannelMap.sys.mjs",
+    "NetworkHelper.sys.mjs",
+    "NetworkObserver.sys.mjs",
+    "NetworkOverride.sys.mjs",
+    "NetworkResponseListener.sys.mjs",
+    "NetworkThrottleManager.sys.mjs",
+    "NetworkUtils.sys.mjs",
+    "WildcardToRegexp.sys.mjs",
+)
diff --git a/devtools/shared/network-observer/test/browser/browser.ini b/devtools/shared/network-observer/test/browser/browser.ini
new file mode 100644
index 0000000000..f1d09d2c1b
--- /dev/null
+++ b/devtools/shared/network-observer/test/browser/browser.ini
@@ -0,0 +1,15 @@
+[DEFAULT]
+tags = devtools
+subsuite = devtools
+support-files =
+  head.js
+  doc_network-observer.html
+  gzipped.sjs
+  override.html
+  override.js
+  sjs_network-observer-test-server.sjs
+
+[browser_networkobserver.js]
+skip-if = http3 # Bug 1829298
+[browser_networkobserver_invalid_constructor.js]
+[browser_networkobserver_override.js]
diff --git a/devtools/shared/network-observer/test/browser/browser_networkobserver.js b/devtools/shared/network-observer/test/browser/browser_networkobserver.js
new file mode 100644
index 0000000000..73e9f8510a
--- /dev/null
+++ b/devtools/shared/network-observer/test/browser/browser_networkobserver.js
@@ -0,0 +1,72 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const TEST_URL = URL_ROOT + "doc_network-observer.html";
+const REQUEST_URL =
+  URL_ROOT + `sjs_network-observer-test-server.sjs?sts=200&fmt=html`;
+
+// Check that the NetworkObserver can detect basic requests and calls the
+// onNetworkEvent callback when expected.
+add_task(async function testSingleRequest() {
+  await addTab(TEST_URL);
+
+  const onNetworkEvents = waitForNetworkEvents(REQUEST_URL, 1);
+  await SpecialPowers.spawn(gBrowser.selectedBrowser, [REQUEST_URL], _url => {
+    content.wrappedJSObject.sendRequest(_url);
+  });
+
+  const eventsCount = await onNetworkEvents;
+  is(eventsCount, 1, "Received the expected number of network events");
+});
+
+add_task(async function testMultipleRequests() {
+  await addTab(TEST_URL);
+  const EXPECTED_REQUESTS_COUNT = 5;
+
+  const onNetworkEvents = waitForNetworkEvents(
+    REQUEST_URL,
+    EXPECTED_REQUESTS_COUNT
+  );
+  await SpecialPowers.spawn(
+    gBrowser.selectedBrowser,
+    [REQUEST_URL, EXPECTED_REQUESTS_COUNT],
+    (_url, _count) => {
+      for (let i = 0; i < _count; i++) {
+        content.wrappedJSObject.sendRequest(_url);
+      }
+    }
+  );
+
+  const eventsCount = await onNetworkEvents;
+  is(
+    eventsCount,
+    EXPECTED_REQUESTS_COUNT,
+    "Received the expected number of network events"
+  );
+});
+
+add_task(async function testOnNetworkEventArguments() {
+  await addTab(TEST_URL);
+
+  const onNetworkEvent = new Promise(resolve => {
+    const networkObserver = new NetworkObserver({
+      ignoreChannelFunction: () => false,
+      onNetworkEvent: (...args) => {
+        resolve(args);
+        return createNetworkEventOwner();
+      },
+    });
+    registerCleanupFunction(() => networkObserver.destroy());
+  });
+
+  await SpecialPowers.spawn(gBrowser.selectedBrowser, [REQUEST_URL], _url => {
+    content.wrappedJSObject.sendRequest(_url);
+  });
+
+  const args = await onNetworkEvent;
+  is(args.length, 2, "Received two arguments");
+  is(typeof args[0], "object", "First argument is an object");
+  ok(args[1] instanceof Ci.nsIChannel, "Second argument is a channel");
+});
diff --git a/devtools/shared/network-observer/test/browser/browser_networkobserver_invalid_constructor.js b/devtools/shared/network-observer/test/browser/browser_networkobserver_invalid_constructor.js
new file mode 100644
index 0000000000..76a93d938a
--- /dev/null
+++ b/devtools/shared/network-observer/test/browser/browser_networkobserver_invalid_constructor.js
@@ -0,0 +1,49 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+// Check that the NetworkObserver constructor validates its arguments.
+add_task(async function testInvalidConstructorArguments() {
+  Assert.throws(
+    () => new NetworkObserver(),
+    /Expected "ignoreChannelFunction" to be a function, got undefined/,
+    "NetworkObserver constructor should throw if no argument was provided"
+  );
+
+  Assert.throws(
+    () => new NetworkObserver({}),
+    /Expected "ignoreChannelFunction" to be a function, got undefined/,
+    "NetworkObserver constructor should throw if ignoreChannelFunction was not provided"
+  );
+
+  const invalidValues = [null, true, false, 12, "str", ["arr"], { obj: "obj" }];
+  for (const invalidValue of invalidValues) {
+    Assert.throws(
+      () => new NetworkObserver({ ignoreChannelFunction: invalidValue }),
+      /Expected "ignoreChannelFunction" to be a function, got/,
+      `NetworkObserver constructor should throw if a(n) ${typeof invalidValue} was provided for ignoreChannelFunction`
+    );
+  }
+
+  const EMPTY_FN = () => {};
+  Assert.throws(
+    () => new NetworkObserver({ ignoreChannelFunction: EMPTY_FN }),
+    /Expected "onNetworkEvent" to be a function, got undefined/,
+    "NetworkObserver constructor should throw if onNetworkEvent was not provided"
+  );
+
+  // Now we will pass a function for `ignoreChannelFunction`, and will do the
+  // same tests for onNetworkEvent
+  for (const invalidValue of invalidValues) {
+    Assert.throws(
+      () =>
+        new NetworkObserver({
+          ignoreChannelFunction: EMPTY_FN,
+          onNetworkEvent: invalidValue,
+        }),
+      /Expected "onNetworkEvent" to be a function, got/,
+      `NetworkObserver constructor should throw if a(n) ${typeof invalidValue} was provided for onNetworkEvent`
+    );
+  }
+});
diff --git a/devtools/shared/network-observer/test/browser/browser_networkobserver_override.js b/devtools/shared/network-observer/test/browser/browser_networkobserver_override.js
new file mode 100644
index 0000000000..3b00c4b2e9
--- /dev/null
+++ b/devtools/shared/network-observer/test/browser/browser_networkobserver_override.js
@@ -0,0 +1,179 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const TEST_URL = URL_ROOT + "doc_network-observer.html";
+const REQUEST_URL =
+  URL_ROOT + `sjs_network-observer-test-server.sjs?sts=200&fmt=html`;
+const GZIPPED_REQUEST_URL = URL_ROOT + `gzipped.sjs`;
+const OVERRIDE_FILENAME = "override.js";
+const OVERRIDE_HTML_FILENAME = "override.html";
+
+add_task(async function testLocalOverride() {
+  await addTab(TEST_URL);
+
+  let eventsCount = 0;
+  const networkObserver = new NetworkObserver({
+    ignoreChannelFunction: channel => channel.URI.spec !== REQUEST_URL,
+    onNetworkEvent: event => {
+      info("received a network event");
+      eventsCount++;
+      return createNetworkEventOwner(event);
+    },
+  });
+
+  const overrideFile = getChromeDir(getResolvedURI(gTestPath));
+  overrideFile.append(OVERRIDE_FILENAME);
+  info(" override " + REQUEST_URL + " to " + overrideFile.path + "\n");
+  networkObserver.override(REQUEST_URL, overrideFile.path);
+
+  info("Assert that request and cached request are overriden");
+  await SpecialPowers.spawn(
+    gBrowser.selectedBrowser,
+    [REQUEST_URL],
+    async _url => {
+      const request = await content.wrappedJSObject.fetch(_url);
+      const requestcontent = await request.text();
+      is(
+        requestcontent,
+        `"use strict";\ndocument.title = "evaluated";\n`,
+        "the request content has been overriden"
+      );
+      const secondRequest = await content.wrappedJSObject.fetch(_url);
+      const secondRequestcontent = await secondRequest.text();
+      is(
+        secondRequestcontent,
+        `"use strict";\ndocument.title = "evaluated";\n`,
+        "the cached request content has been overriden"
+      );
+    }
+  );
+
+  info("Assert that JS scripts can be overriden");
+  await SpecialPowers.spawn(
+    gBrowser.selectedBrowser,
+    [REQUEST_URL],
+    async _url => {
+      const script = await content.document.createElement("script");
+      const onLoad = new Promise(resolve =>
+        script.addEventListener("load", resolve, { once: true })
+      );
+      script.src = _url;
+      content.document.body.appendChild(script);
+      await onLoad;
+      is(
+        content.document.title,
+        "evaluated",
+        "The <script> tag content has been overriden and correctly evaluated"
+      );
+    }
+  );
+
+  await BrowserTestUtils.waitForCondition(() => eventsCount >= 1);
+
+  networkObserver.destroy();
+});
+
+add_task(async function testHtmlFileOverride() {
+  let eventsCount = 0;
+  const networkObserver = new NetworkObserver({
+    ignoreChannelFunction: channel => channel.URI.spec !== TEST_URL,
+    onNetworkEvent: event => {
+      info("received a network event");
+      eventsCount++;
+      return createNetworkEventOwner(event);
+    },
+  });
+
+  const overrideFile = getChromeDir(getResolvedURI(gTestPath));
+  overrideFile.append(OVERRIDE_HTML_FILENAME);
+  info(" override " + TEST_URL + " to " + overrideFile.path + "\n");
+  networkObserver.override(TEST_URL, overrideFile.path);
+
+  await addTab(TEST_URL);
+  await SpecialPowers.spawn(
+    gBrowser.selectedBrowser,
+    [TEST_URL],
+    async pageUrl => {
+      is(
+        content.document.documentElement.outerHTML,
+        "<html><head></head><body>Overriden!\n</body></html>",
+        "The content of the HTML has been overriden"
+      );
+      // For now, all overriden request have their location changed to an internal data: URI
+      // Bug xxx aims at keeping the original URI.
+      todo_is(
+        content.location.href,
+        pageUrl,
+        "The location of the page is still the original one"
+      );
+    }
+  );
+  await BrowserTestUtils.waitForCondition(() => eventsCount >= 1);
+  networkObserver.destroy();
+});
+
+// Exact same test, but with a gzipped request, which requires very special treatment
+add_task(async function testLocalOverrideGzipped() {
+  await addTab(TEST_URL);
+
+  let eventsCount = 0;
+  const networkObserver = new NetworkObserver({
+    ignoreChannelFunction: channel => channel.URI.spec !== GZIPPED_REQUEST_URL,
+    onNetworkEvent: event => {
+      info("received a network event");
+      eventsCount++;
+      return createNetworkEventOwner(event);
+    },
+  });
+
+  const overrideFile = getChromeDir(getResolvedURI(gTestPath));
+  overrideFile.append(OVERRIDE_FILENAME);
+  info(" override " + GZIPPED_REQUEST_URL + " to " + overrideFile.path + "\n");
+  networkObserver.override(GZIPPED_REQUEST_URL, overrideFile.path);
+
+  await SpecialPowers.spawn(
+    gBrowser.selectedBrowser,
+    [GZIPPED_REQUEST_URL],
+    async _url => {
+      const request = await content.wrappedJSObject.fetch(_url);
+      const requestcontent = await request.text();
+      is(
+        requestcontent,
+        `"use strict";\ndocument.title = "evaluated";\n`,
+        "the request content has been overriden"
+      );
+      const secondRequest = await content.wrappedJSObject.fetch(_url);
+      const secondRequestcontent = await secondRequest.text();
+      is(
+        secondRequestcontent,
+        `"use strict";\ndocument.title = "evaluated";\n`,
+        "the cached request content has been overriden"
+      );
+    }
+  );
+
+  await SpecialPowers.spawn(
+    gBrowser.selectedBrowser,
+    [GZIPPED_REQUEST_URL],
+    async _url => {
+      const script = await content.document.createElement("script");
+      const onLoad = new Promise(resolve =>
+        script.addEventListener("load", resolve, { once: true })
+      );
+      script.src = _url;
+      content.document.body.appendChild(script);
+      await onLoad;
+      is(
+        content.document.title,
+        "evaluated",
+        "The <script> tag content has been overriden and correctly evaluated"
+      );
+    }
+  );
+
+  await BrowserTestUtils.waitForCondition(() => eventsCount >= 1);
+
+  networkObserver.destroy();
+});
diff --git a/devtools/shared/network-observer/test/browser/doc_network-observer.html b/devtools/shared/network-observer/test/browser/doc_network-observer.html
new file mode 100644
index 0000000000..90cd9be69b
--- /dev/null
+++ b/devtools/shared/network-observer/test/browser/doc_network-observer.html
@@ -0,0 +1,25 @@
+<!-- Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/ -->
+<!doctype html>
+
+<html>
+  <head>
+    <meta charset="utf-8"/>
+    <meta http-equiv="Cache-Control" content="no-cache, no-store, must-revalidate" />
+    <meta http-equiv="Pragma" content="no-cache" />
+    <meta http-equiv="Expires" content="0" />
+    <title>Network Observer test page</title>
+  </head>
+  <body>
+    <p>Network Observer test page</p>
+    <script type="text/javascript">
+      "use strict";
+
+      window.sendRequest = url => {
+        const xhr = new XMLHttpRequest();
+        xhr.open("GET", url, true);
+        xhr.send(null);
+      }
+    </script>
+  </body>
+</html>
diff --git a/devtools/shared/network-observer/test/browser/gzipped.sjs b/devtools/shared/network-observer/test/browser/gzipped.sjs
new file mode 100644
index 0000000000..09d0b249b1
--- /dev/null
+++ b/devtools/shared/network-observer/test/browser/gzipped.sjs
@@ -0,0 +1,44 @@
+"use strict";
+
+function gzipCompressString(string, obs) {
+  const scs = Cc["@mozilla.org/streamConverters;1"].getService(
+    Ci.nsIStreamConverterService
+  );
+  const listener = Cc["@mozilla.org/network/stream-loader;1"].createInstance(
+    Ci.nsIStreamLoader
+  );
+  listener.init(obs);
+  const converter = scs.asyncConvertData(
+    "uncompressed",
+    "gzip",
+    listener,
+    null
+  );
+  const stringStream = Cc[
+    "@mozilla.org/io/string-input-stream;1"
+  ].createInstance(Ci.nsIStringInputStream);
+  stringStream.data = string;
+  converter.onStartRequest(null, null);
+  converter.onDataAvailable(null, stringStream, 0, string.length);
+  converter.onStopRequest(null, null, null);
+}
+
+const ORIGINAL_JS_CONTENT = `console.log("original javascript content");`;
+
+function handleRequest(request, response) {
+  response.processAsync();
+
+  // Generate data
+  response.setHeader("Content-Type", "application/javascript", false);
+  response.setHeader("Content-Encoding", "gzip", false);
+
+  const observer = {
+    onStreamComplete(loader, context, status, length, result) {
+      const buffer = String.fromCharCode.apply(this, result);
+      response.setHeader("Content-Length", "" + buffer.length, false);
+      response.write(buffer);
+      response.finish();
+    },
+  };
+  gzipCompressString(ORIGINAL_JS_CONTENT, observer);
+}
diff --git a/devtools/shared/network-observer/test/browser/head.js b/devtools/shared/network-observer/test/browser/head.js
new file mode 100644
index 0000000000..ab03163d9d
--- /dev/null
+++ b/devtools/shared/network-observer/test/browser/head.js
@@ -0,0 +1,92 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  NetworkObserver:
+    "resource://devtools/shared/network-observer/NetworkObserver.sys.mjs",
+});
+
+const TEST_DIR = gTestPath.substr(0, gTestPath.lastIndexOf("/"));
+const CHROME_URL_ROOT = TEST_DIR + "/";
+const URL_ROOT = CHROME_URL_ROOT.replace(
+  "chrome://mochitests/content/",
+  "https://example.com/"
+);
+
+/**
+ * Load the provided url in an existing browser.
+ * Returns a promise which will resolve when the page is loaded.
+ *
+ * @param {Browser} browser
+ *     The browser element where the URL should be loaded.
+ * @param {String} url
+ *     The URL to load in the new tab
+ */
+async function loadURL(browser, url) {
+  const loaded = BrowserTestUtils.browserLoaded(browser);
+  BrowserTestUtils.loadURIString(browser, url);
+  return loaded;
+}
+
+/**
+ * Create a new foreground tab loading the provided url.
+ * Returns a promise which will resolve when the page is loaded.
+ *
+ * @param {String} url
+ *     The URL to load in the new tab
+ */
+async function addTab(url) {
+  const tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, url);
+  registerCleanupFunction(() => {
+    gBrowser.removeTab(tab);
+  });
+  return tab;
+}
+
+/**
+ * Create a simple network event owner, with empty implementations of all
+ * the expected APIs for a NetworkEventOwner.
+ */
+function createNetworkEventOwner(event) {
+  return {
+    addEventTimings: () => {},
+    addResponseCache: () => {},
+    addResponseContent: () => {},
+    addResponseStart: () => {},
+    addSecurityInfo: () => {},
+    addServerTimings: () => {},
+  };
+}
+
+/**
+ * Wait for network events matching the provided URL, until the count reaches
+ * the provided expected count.
+ *
+ * @param {string} expectedUrl
+ *     The URL which should be monitored by the NetworkObserver.
+ * @param {number} expectedRequestsCount
+ *     How many different events (requests) are expected.
+ * @returns {Promise}
+ *     A promise which will resolve with the current count, when the expected
+ *     count is reached.
+ */
+async function waitForNetworkEvents(expectedUrl, expectedRequestsCount) {
+  let eventsCount = 0;
+  const networkObserver = new NetworkObserver({
+    ignoreChannelFunction: channel => channel.URI.spec !== expectedUrl,
+    onNetworkEvent: event => {
+      info("waitForNetworkEvents received a new event");
+      eventsCount++;
+      return createNetworkEventOwner(event);
+    },
+  });
+  registerCleanupFunction(() => networkObserver.destroy());
+
+  info("Wait until the events count reaches " + expectedRequestsCount);
+  await BrowserTestUtils.waitForCondition(
+    () => eventsCount >= expectedRequestsCount
+  );
+  return eventsCount;
+}
diff --git a/devtools/shared/network-observer/test/browser/override.html b/devtools/shared/network-observer/test/browser/override.html
new file mode 100644
index 0000000000..0e3878e313
--- /dev/null
+++ b/devtools/shared/network-observer/test/browser/override.html
@@ -0,0 +1 @@
+<html><head></head><body>Overriden!</body></html>
diff --git a/devtools/shared/network-observer/test/browser/override.js b/devtools/shared/network-observer/test/browser/override.js
new file mode 100644
index 0000000000..7b000fcd0f
--- /dev/null
+++ b/devtools/shared/network-observer/test/browser/override.js
@@ -0,0 +1,2 @@
+"use strict";
+document.title = "evaluated";
diff --git a/devtools/shared/network-observer/test/browser/sjs_network-observer-test-server.sjs b/devtools/shared/network-observer/test/browser/sjs_network-observer-test-server.sjs
new file mode 100644
index 0000000000..918d6e8447
--- /dev/null
+++ b/devtools/shared/network-observer/test/browser/sjs_network-observer-test-server.sjs
@@ -0,0 +1,198 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+Cu.importGlobalProperties(["TextEncoder"]);
+
+// Simple server which can handle several response types and states.
+// Trimmed down from devtools/client/netmonitor/test/sjs_content-type-test-server.sjs
+// Additional features can be ported if needed.
+function handleRequest(request, response) {
+  response.processAsync();
+
+  const params = request.queryString.split("&");
+  const format = (params.filter(s => s.includes("fmt="))[0] || "").split(
+    "="
+  )[1];
+  const status =
+    (params.filter(s => s.includes("sts="))[0] || "").split("=")[1] || 200;
+
+  const cacheExpire = 60; // seconds
+
+  function setCacheHeaders() {
+    if (status != 304) {
+      response.setHeader(
+        "Cache-Control",
+        "no-cache, no-store, must-revalidate"
+      );
+      response.setHeader("Pragma", "no-cache");
+      response.setHeader("Expires", "0");
+      return;
+    }
+
+    response.setHeader("Expires", Date(Date.now() + cacheExpire * 1000), false);
+  }
+
+  let timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
+
+  timer.initWithCallback(
+    // eslint-disable-next-line complexity
+    () => {
+      // to avoid garbage collection
+      timer = null;
+      switch (format) {
+        case "txt": {
+          response.setStatusLine(request.httpVersion, status, "DA DA DA");
+          response.setHeader("Content-Type", "text/plain", false);
+          setCacheHeaders();
+
+          function convertToUtf8(str) {
+            return String.fromCharCode(...new TextEncoder().encode(str));
+          }
+
+          // This script must be evaluated as UTF-8 for this to write out the
+          // bytes of the string in UTF-8.  If it's evaluated as Latin-1, the
+          // written bytes will be the result of UTF-8-encoding this string
+          // *twice*.
+          const data = "Братан, ты вообще качаешься?";
+          const stringOfUtf8Bytes = convertToUtf8(data);
+          response.write(stringOfUtf8Bytes);
+
+          response.finish();
+          break;
+        }
+        case "xml": {
+          response.setStatusLine(request.httpVersion, status, "OK");
+          response.setHeader("Content-Type", "text/xml; charset=utf-8", false);
+          setCacheHeaders();
+          response.write("<label value='greeting'>Hello XML!</label>");
+          response.finish();
+          break;
+        }
+        case "html": {
+          const content = (
+            params.filter(s => s.includes("res="))[0] || ""
+          ).split("=")[1];
+          response.setStatusLine(request.httpVersion, status, "OK");
+          response.setHeader("Content-Type", "text/html; charset=utf-8", false);
+          setCacheHeaders();
+          response.write(content || "<p>Hello HTML!</p>");
+          response.finish();
+          break;
+        }
+        case "xhtml": {
+          response.setStatusLine(request.httpVersion, status, "OK");
+          response.setHeader(
+            "Content-Type",
+            "application/xhtml+xml; charset=utf-8",
+            false
+          );
+          setCacheHeaders();
+          response.write("<p>Hello XHTML!</p>");
+          response.finish();
+          break;
+        }
+        case "html-long": {
+          const str = new Array(102400 /* 100 KB in bytes */).join(".");
+          response.setStatusLine(request.httpVersion, status, "OK");
+          response.setHeader("Content-Type", "text/html; charset=utf-8", false);
+          setCacheHeaders();
+          response.write("<p>" + str + "</p>");
+          response.finish();
+          break;
+        }
+        case "css": {
+          response.setStatusLine(request.httpVersion, status, "OK");
+          response.setHeader("Content-Type", "text/css; charset=utf-8", false);
+          setCacheHeaders();
+          response.write("body:pre { content: 'Hello CSS!' }");
+          response.finish();
+          break;
+        }
+        case "js": {
+          response.setStatusLine(request.httpVersion, status, "OK");
+          response.setHeader(
+            "Content-Type",
+            "application/javascript; charset=utf-8",
+            false
+          );
+          setCacheHeaders();
+          response.write("function() { return 'Hello JS!'; }");
+          response.finish();
+          break;
+        }
+        case "json": {
+          response.setStatusLine(request.httpVersion, status, "OK");
+          response.setHeader(
+            "Content-Type",
+            "application/json; charset=utf-8",
+            false
+          );
+          setCacheHeaders();
+          response.write('{ "greeting": "Hello JSON!" }');
+          response.finish();
+          break;
+        }
+
+        case "font": {
+          response.setStatusLine(request.httpVersion, status, "OK");
+          response.setHeader("Content-Type", "font/woff", false);
+          setCacheHeaders();
+          response.finish();
+          break;
+        }
+        case "image": {
+          response.setStatusLine(request.httpVersion, status, "OK");
+          response.setHeader("Content-Type", "image/png", false);
+          setCacheHeaders();
+          response.finish();
+          break;
+        }
+        case "application-ogg": {
+          response.setStatusLine(request.httpVersion, status, "OK");
+          response.setHeader("Content-Type", "application/ogg", false);
+          setCacheHeaders();
+          response.finish();
+          break;
+        }
+        case "audio": {
+          response.setStatusLine(request.httpVersion, status, "OK");
+          response.setHeader("Content-Type", "audio/ogg", false);
+          setCacheHeaders();
+          response.finish();
+          break;
+        }
+        case "video": {
+          response.setStatusLine(request.httpVersion, status, "OK");
+          response.setHeader("Content-Type", "video/webm", false);
+          setCacheHeaders();
+          response.finish();
+          break;
+        }
+        case "ws": {
+          response.setStatusLine(
+            request.httpVersion,
+            101,
+            "Switching Protocols"
+          );
+          response.setHeader("Connection", "upgrade", false);
+          response.setHeader("Upgrade", "websocket", false);
+          setCacheHeaders();
+          response.finish();
+          break;
+        }
+        default: {
+          response.setStatusLine(request.httpVersion, 404, "Not Found");
+          response.setHeader("Content-Type", "text/html; charset=utf-8", false);
+          setCacheHeaders();
+          response.write("<blink>Not Found</blink>");
+          response.finish();
+          break;
+        }
+      }
+    },
+    10,
+    Ci.nsITimer.TYPE_ONE_SHOT
+  ); // Make sure this request takes a few ms.
+}
diff --git a/devtools/shared/network-observer/test/xpcshell/head.js b/devtools/shared/network-observer/test/xpcshell/head.js
new file mode 100644
index 0000000000..93b66e4632
--- /dev/null
+++ b/devtools/shared/network-observer/test/xpcshell/head.js
@@ -0,0 +1,9 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  NetworkHelper:
+    "resource://devtools/shared/network-observer/NetworkHelper.sys.mjs",
+});
diff --git a/devtools/shared/network-observer/test/xpcshell/test_network_helper.js b/devtools/shared/network-observer/test/xpcshell/test_network_helper.js
new file mode 100644
index 0000000000..ff514ab98e
--- /dev/null
+++ b/devtools/shared/network-observer/test/xpcshell/test_network_helper.js
@@ -0,0 +1,90 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+function run_test() {
+  test_isTextMimeType();
+  test_parseCookieHeader();
+}
+
+function test_isTextMimeType() {
+  Assert.equal(NetworkHelper.isTextMimeType("text/plain"), true);
+  Assert.equal(NetworkHelper.isTextMimeType("application/javascript"), true);
+  Assert.equal(NetworkHelper.isTextMimeType("application/json"), true);
+  Assert.equal(NetworkHelper.isTextMimeType("text/css"), true);
+  Assert.equal(NetworkHelper.isTextMimeType("text/html"), true);
+  Assert.equal(NetworkHelper.isTextMimeType("image/svg+xml"), true);
+  Assert.equal(NetworkHelper.isTextMimeType("application/xml"), true);
+
+  // Test custom JSON subtype
+  Assert.equal(
+    NetworkHelper.isTextMimeType("application/vnd.tent.posts-feed.v0+json"),
+    true
+  );
+  Assert.equal(
+    NetworkHelper.isTextMimeType("application/vnd.tent.posts-feed.v0-json"),
+    true
+  );
+  // Test custom XML subtype
+  Assert.equal(
+    NetworkHelper.isTextMimeType("application/vnd.tent.posts-feed.v0+xml"),
+    true
+  );
+  Assert.equal(
+    NetworkHelper.isTextMimeType("application/vnd.tent.posts-feed.v0-xml"),
+    false
+  );
+  // Test case-insensitive
+  Assert.equal(
+    NetworkHelper.isTextMimeType("application/vnd.BIG-CORP+json"),
+    true
+  );
+  // Test non-text type
+  Assert.equal(NetworkHelper.isTextMimeType("image/png"), false);
+  // Test invalid types
+  Assert.equal(NetworkHelper.isTextMimeType("application/foo-+json"), false);
+  Assert.equal(NetworkHelper.isTextMimeType("application/-foo+json"), false);
+  Assert.equal(
+    NetworkHelper.isTextMimeType("application/foo--bar+json"),
+    false
+  );
+
+  // Test we do not cause internal errors with unoptimized regex. Bug 961097
+  Assert.equal(
+    NetworkHelper.isTextMimeType("application/vnd.google.safebrowsing-chunk"),
+    false
+  );
+}
+
+function test_parseCookieHeader() {
+  let result = NetworkHelper.parseSetCookieHeaders(["Test=1; SameSite=Strict"]);
+  Assert.deepEqual(result, [{ name: "Test", value: "1", samesite: "Strict" }]);
+
+  result = NetworkHelper.parseSetCookieHeaders(["Test=1; SameSite=strict"]);
+  Assert.deepEqual(result, [{ name: "Test", value: "1", samesite: "Strict" }]);
+
+  result = NetworkHelper.parseSetCookieHeaders(["Test=1; SameSite=STRICT"]);
+  Assert.deepEqual(result, [{ name: "Test", value: "1", samesite: "Strict" }]);
+
+  result = NetworkHelper.parseSetCookieHeaders(["Test=1; SameSite=None"]);
+  Assert.deepEqual(result, [{ name: "Test", value: "1", samesite: "None" }]);
+
+  result = NetworkHelper.parseSetCookieHeaders(["Test=1; SameSite=NONE"]);
+  Assert.deepEqual(result, [{ name: "Test", value: "1", samesite: "None" }]);
+
+  result = NetworkHelper.parseSetCookieHeaders(["Test=1; SameSite=lax"]);
+  Assert.deepEqual(result, [{ name: "Test", value: "1", samesite: "Lax" }]);
+
+  result = NetworkHelper.parseSetCookieHeaders(["Test=1; SameSite=Lax"]);
+  Assert.deepEqual(result, [{ name: "Test", value: "1", samesite: "Lax" }]);
+
+  result = NetworkHelper.parseSetCookieHeaders([
+    "Test=1; SameSite=Lax",
+    "Foo=2; SameSite=None",
+  ]);
+  Assert.deepEqual(result, [
+    { name: "Test", value: "1", samesite: "Lax" },
+    { name: "Foo", value: "2", samesite: "None" },
+  ]);
+}
diff --git a/devtools/shared/network-observer/test/xpcshell/test_security-info-certificate.js b/devtools/shared/network-observer/test/xpcshell/test_security-info-certificate.js
new file mode 100644
index 0000000000..00f482b8ca
--- /dev/null
+++ b/devtools/shared/network-observer/test/xpcshell/test_security-info-certificate.js
@@ -0,0 +1,84 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+"use strict";
+
+// Tests that NetworkHelper.parseCertificateInfo parses certificate information
+// correctly.
+
+const DUMMY_CERT = {
+  getBase64DERString() {
+    // This is the base64-encoded contents of the "DigiCert ECC Secure Server CA"
+    // intermediate certificate as issued by "DigiCert Global Root CA". It was
+    // chosen as a test certificate because it has an issuer common name,
+    // organization, and organizational unit that are somewhat distinct from
+    // its subject common name and organization name.
+    return "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";
+  },
+};
+
+add_task(async function run_test() {
+  info("Testing NetworkHelper.parseCertificateInfo.");
+
+  const result = await NetworkHelper.parseCertificateInfo(
+    DUMMY_CERT,
+    new Map()
+  );
+
+  // Subject
+  equal(
+    result.subject.commonName,
+    "DigiCert ECC Secure Server CA",
+    "Common name is correct."
+  );
+  equal(
+    result.subject.organization,
+    "DigiCert Inc",
+    "Organization is correct."
+  );
+  equal(
+    result.subject.organizationUnit,
+    undefined,
+    "Organizational unit is correct."
+  );
+
+  // Issuer
+  equal(
+    result.issuer.commonName,
+    "DigiCert Global Root CA",
+    "Common name of the issuer is correct."
+  );
+  equal(
+    result.issuer.organization,
+    "DigiCert Inc",
+    "Organization of the issuer is correct."
+  );
+  equal(
+    result.issuer.organizationUnit,
+    "www.digicert.com",
+    "Organizational unit of the issuer is correct."
+  );
+
+  // Validity
+  equal(
+    result.validity.start,
+    "Fri, 08 Mar 2013 12:00:00 GMT",
+    "Start of the validity period is correct."
+  );
+  equal(
+    result.validity.end,
+    "Wed, 08 Mar 2023 12:00:00 GMT",
+    "End of the validity period is correct."
+  );
+
+  // Fingerprints
+  equal(
+    result.fingerprint.sha1,
+    "56:EE:7C:27:06:83:16:2D:83:BA:EA:CC:79:0E:22:47:1A:DA:AB:E8",
+    "Certificate SHA1 fingerprint is correct."
+  );
+  equal(
+    result.fingerprint.sha256,
+    "45:84:46:BA:75:D9:32:E9:14:F2:3C:2B:57:B7:D1:92:ED:DB:C2:18:1D:95:8E:11:81:AD:52:51:74:7A:1E:E8",
+    "Certificate SHA256 fingerprint is correct."
+  );
+});
diff --git a/devtools/shared/network-observer/test/xpcshell/test_security-info-parser.js b/devtools/shared/network-observer/test/xpcshell/test_security-info-parser.js
new file mode 100644
index 0000000000..9515851a8b
--- /dev/null
+++ b/devtools/shared/network-observer/test/xpcshell/test_security-info-parser.js
@@ -0,0 +1,54 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+"use strict";
+
+// Test that NetworkHelper.parseSecurityInfo returns correctly formatted object.
+
+const wpl = Ci.nsIWebProgressListener;
+const MockCertificate = {
+  getBase64DERString() {
+    // This is the same test certificate as in
+    // test_security-info-certificate.js for consistency.
+    return "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";
+  },
+};
+
+// This *cannot* be used as an nsITransportSecurityInfo (since that interface is
+// builtinclass) but the methods being tested aren't defined by XPCOM and aren't
+// calling QueryInterface, so this usage is fine.
+const MockSecurityInfo = {
+  securityState: wpl.STATE_IS_SECURE,
+  errorCode: 0,
+  cipherName: "TLS_ECDH_ECDSA_WITH_AES_128_GCM_SHA256",
+  // TLS_VERSION_1_2
+  protocolVersion: 3,
+  serverCert: MockCertificate,
+};
+
+add_task(async function run_test() {
+  const result = await NetworkHelper.parseSecurityInfo(
+    MockSecurityInfo,
+    {},
+    {},
+    new Map()
+  );
+
+  equal(result.state, "secure", "State is correct.");
+
+  equal(
+    result.cipherSuite,
+    MockSecurityInfo.cipherName,
+    "Cipher suite is correct."
+  );
+
+  equal(result.protocolVersion, "TLSv1.2", "Protocol version is correct.");
+
+  deepEqual(
+    result.cert,
+    await NetworkHelper.parseCertificateInfo(MockCertificate, new Map()),
+    "Certificate information is correct."
+  );
+
+  equal(result.hpkp, false, "HPKP is false when URI is not available.");
+  equal(result.hsts, false, "HSTS is false when URI is not available.");
+});
diff --git a/devtools/shared/network-observer/test/xpcshell/test_security-info-protocol-version.js b/devtools/shared/network-observer/test/xpcshell/test_security-info-protocol-version.js
new file mode 100644
index 0000000000..a81f7ce73c
--- /dev/null
+++ b/devtools/shared/network-observer/test/xpcshell/test_security-info-protocol-version.js
@@ -0,0 +1,48 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+"use strict";
+
+// Tests that NetworkHelper.formatSecurityProtocol returns correct
+// protocol version strings.
+
+const TEST_CASES = [
+  {
+    description: "TLS_VERSION_1",
+    input: 1,
+    expected: "TLSv1",
+  },
+  {
+    description: "TLS_VERSION_1.1",
+    input: 2,
+    expected: "TLSv1.1",
+  },
+  {
+    description: "TLS_VERSION_1.2",
+    input: 3,
+    expected: "TLSv1.2",
+  },
+  {
+    description: "TLS_VERSION_1.3",
+    input: 4,
+    expected: "TLSv1.3",
+  },
+  {
+    description: "invalid version",
+    input: -1,
+    expected: "Unknown",
+  },
+];
+
+function run_test() {
+  info("Testing NetworkHelper.formatSecurityProtocol.");
+
+  for (const { description, input, expected } of TEST_CASES) {
+    info("Testing " + description);
+
+    equal(
+      NetworkHelper.formatSecurityProtocol(input),
+      expected,
+      "Got the expected protocol string."
+    );
+  }
+}
diff --git a/devtools/shared/network-observer/test/xpcshell/test_security-info-state.js b/devtools/shared/network-observer/test/xpcshell/test_security-info-state.js
new file mode 100644
index 0000000000..be622b2019
--- /dev/null
+++ b/devtools/shared/network-observer/test/xpcshell/test_security-info-state.js
@@ -0,0 +1,122 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+"use strict";
+
+// Tests that security info parser gives correct general security state for
+// different cases.
+
+const wpl = Ci.nsIWebProgressListener;
+
+// This *cannot* be used as an nsITransportSecurityInfo (since that interface is
+// builtinclass) but the methods being tested aren't defined by XPCOM and aren't
+// calling QueryInterface, so this usage is fine.
+const MockSecurityInfo = {
+  securityState: wpl.STATE_IS_BROKEN,
+  errorCode: 0,
+  // nsISSLStatus.TLS_VERSION_1_2
+  protocolVersion: 3,
+  cipherName: "TLS_ECDH_ECDSA_WITH_AES_128_GCM_SHA256",
+};
+
+add_task(async function run_test() {
+  await test_nullSecurityInfo();
+  await test_insecureSecurityInfoWithNSSError();
+  await test_insecureSecurityInfoWithoutNSSError();
+  await test_brokenSecurityInfo();
+  await test_secureSecurityInfo();
+});
+
+/**
+ * Test that undefined security information is returns "insecure".
+ */
+async function test_nullSecurityInfo() {
+  const result = await NetworkHelper.parseSecurityInfo(null, {}, {}, new Map());
+  equal(
+    result.state,
+    "insecure",
+    "state == 'insecure' when securityInfo was undefined"
+  );
+}
+
+/**
+ * Test that STATE_IS_INSECURE with NSSError returns "broken"
+ */
+async function test_insecureSecurityInfoWithNSSError() {
+  MockSecurityInfo.securityState = wpl.STATE_IS_INSECURE;
+
+  // Taken from security/manager/ssl/tests/unit/head_psm.js.
+  MockSecurityInfo.errorCode = -8180;
+
+  const result = await NetworkHelper.parseSecurityInfo(
+    MockSecurityInfo,
+    {},
+    {},
+    new Map()
+  );
+  equal(
+    result.state,
+    "broken",
+    "state == 'broken' if securityState contains STATE_IS_INSECURE flag AND " +
+      "errorCode is NSS error."
+  );
+
+  MockSecurityInfo.errorCode = 0;
+}
+
+/**
+ * Test that STATE_IS_INSECURE without NSSError returns "insecure"
+ */
+async function test_insecureSecurityInfoWithoutNSSError() {
+  MockSecurityInfo.securityState = wpl.STATE_IS_INSECURE;
+
+  const result = await NetworkHelper.parseSecurityInfo(
+    MockSecurityInfo,
+    {},
+    {},
+    new Map()
+  );
+  equal(
+    result.state,
+    "insecure",
+    "state == 'insecure' if securityState contains STATE_IS_INSECURE flag BUT " +
+      "errorCode is not NSS error."
+  );
+}
+
+/**
+ * Test that STATE_IS_SECURE returns "secure"
+ */
+async function test_secureSecurityInfo() {
+  MockSecurityInfo.securityState = wpl.STATE_IS_SECURE;
+
+  const result = await NetworkHelper.parseSecurityInfo(
+    MockSecurityInfo,
+    {},
+    {},
+    new Map()
+  );
+  equal(
+    result.state,
+    "secure",
+    "state == 'secure' if securityState contains STATE_IS_SECURE flag"
+  );
+}
+
+/**
+ * Test that STATE_IS_BROKEN returns "weak"
+ */
+async function test_brokenSecurityInfo() {
+  MockSecurityInfo.securityState = wpl.STATE_IS_BROKEN;
+
+  const result = await NetworkHelper.parseSecurityInfo(
+    MockSecurityInfo,
+    {},
+    {},
+    new Map()
+  );
+  equal(
+    result.state,
+    "weak",
+    "state == 'weak' if securityState contains STATE_IS_BROKEN flag"
+  );
+}
diff --git a/devtools/shared/network-observer/test/xpcshell/test_security-info-static-hpkp.js b/devtools/shared/network-observer/test/xpcshell/test_security-info-static-hpkp.js
new file mode 100644
index 0000000000..f1aa883b93
--- /dev/null
+++ b/devtools/shared/network-observer/test/xpcshell/test_security-info-static-hpkp.js
@@ -0,0 +1,41 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+"use strict";
+
+// Test that NetworkHelper.parseSecurityInfo correctly detects static hpkp pins
+
+const wpl = Ci.nsIWebProgressListener;
+
+// This *cannot* be used as an nsITransportSecurityInfo (since that interface is
+// builtinclass) but the methods being tested aren't defined by XPCOM and aren't
+// calling QueryInterface, so this usage is fine.
+const MockSecurityInfo = {
+  securityState: wpl.STATE_IS_SECURE,
+  errorCode: 0,
+  cipherName: "TLS_ECDH_ECDSA_WITH_AES_128_GCM_SHA256",
+  // TLS_VERSION_1_2
+  protocolVersion: 3,
+  serverCert: {
+    getBase64DERString() {
+      // This is the same test certificate as in
+      // test_security-info-certificate.js for consistency.
+      return "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";
+    },
+  },
+};
+
+const MockHttpInfo = {
+  hostname: "include-subdomains.pinning.example.com",
+  private: false,
+};
+
+add_task(async function run_test() {
+  Services.prefs.setIntPref("security.cert_pinning.enforcement_level", 1);
+  const result = await NetworkHelper.parseSecurityInfo(
+    MockSecurityInfo,
+    {},
+    MockHttpInfo,
+    new Map()
+  );
+  equal(result.hpkp, true, "Static HPKP detected.");
+});
diff --git a/devtools/shared/network-observer/test/xpcshell/test_security-info-weakness-reasons.js b/devtools/shared/network-observer/test/xpcshell/test_security-info-weakness-reasons.js
new file mode 100644
index 0000000000..71d7675284
--- /dev/null
+++ b/devtools/shared/network-observer/test/xpcshell/test_security-info-weakness-reasons.js
@@ -0,0 +1,39 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+"use strict";
+
+// Tests that NetworkHelper.getReasonsForWeakness returns correct reasons for
+// weak requests.
+
+const wpl = Ci.nsIWebProgressListener;
+const TEST_CASES = [
+  {
+    description: "weak cipher",
+    input: wpl.STATE_IS_BROKEN | wpl.STATE_USES_WEAK_CRYPTO,
+    expected: ["cipher"],
+  },
+  {
+    description: "only STATE_IS_BROKEN flag",
+    input: wpl.STATE_IS_BROKEN,
+    expected: [],
+  },
+  {
+    description: "only STATE_IS_SECURE flag",
+    input: wpl.STATE_IS_SECURE,
+    expected: [],
+  },
+];
+
+function run_test() {
+  info("Testing NetworkHelper.getReasonsForWeakness.");
+
+  for (const { description, input, expected } of TEST_CASES) {
+    info("Testing " + description);
+
+    deepEqual(
+      NetworkHelper.getReasonsForWeakness(input),
+      expected,
+      "Got the expected reasons for weakness."
+    );
+  }
+}
diff --git a/devtools/shared/network-observer/test/xpcshell/test_throttle.js b/devtools/shared/network-observer/test/xpcshell/test_throttle.js
new file mode 100644
index 0000000000..5f8ef589fb
--- /dev/null
+++ b/devtools/shared/network-observer/test/xpcshell/test_throttle.js
@@ -0,0 +1,162 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+/* eslint-disable mozilla/use-chromeutils-generateqi */
+
+const { NetworkThrottleManager } = ChromeUtils.importESModule(
+  "resource://devtools/shared/network-observer/NetworkThrottleManager.sys.mjs"
+);
+const nsIScriptableInputStream = Ci.nsIScriptableInputStream;
+
+function TestStreamListener() {
+  this.state = "initial";
+}
+TestStreamListener.prototype = {
+  onStartRequest() {
+    this.setState("start");
+  },
+
+  onStopRequest() {
+    this.setState("stop");
+  },
+
+  onDataAvailable(request, inputStream, offset, count) {
+    const sin = Cc["@mozilla.org/scriptableinputstream;1"].createInstance(
+      nsIScriptableInputStream
+    );
+    sin.init(inputStream);
+    this.data = sin.read(count);
+    this.setState("data");
+  },
+
+  setState(state) {
+    this.state = state;
+    if (this._deferred) {
+      this._deferred.resolve(state);
+      this._deferred = null;
+    }
+  },
+
+  onStateChanged() {
+    if (!this._deferred) {
+      let resolve, reject;
+      const promise = new Promise(function (res, rej) {
+        resolve = res;
+        reject = rej;
+      });
+      this._deferred = { resolve, reject, promise };
+    }
+    return this._deferred.promise;
+  },
+};
+
+function TestChannel() {
+  this.state = "initial";
+  this.testListener = new TestStreamListener();
+  this._throttleQueue = null;
+}
+TestChannel.prototype = {
+  QueryInterface() {
+    return this;
+  },
+
+  get throttleQueue() {
+    return this._throttleQueue;
+  },
+
+  set throttleQueue(q) {
+    this._throttleQueue = q;
+    this.state = "throttled";
+  },
+
+  setNewListener(listener) {
+    this.listener = listener;
+    this.state = "listener";
+    return this.testListener;
+  },
+};
+
+add_task(async function () {
+  const throttler = new NetworkThrottleManager({
+    latencyMean: 1,
+    latencyMax: 1,
+    downloadBPSMean: 500,
+    downloadBPSMax: 500,
+    uploadBPSMean: 500,
+    uploadBPSMax: 500,
+  });
+
+  const uploadChannel = new TestChannel();
+  throttler.manageUpload(uploadChannel);
+  equal(
+    uploadChannel.state,
+    "throttled",
+    "NetworkThrottleManager set throttleQueue"
+  );
+
+  const downloadChannel = new TestChannel();
+  const testListener = downloadChannel.testListener;
+
+  const listener = throttler.manage(downloadChannel);
+  equal(
+    downloadChannel.state,
+    "listener",
+    "NetworkThrottleManager called setNewListener"
+  );
+
+  equal(testListener.state, "initial", "test listener in initial state");
+
+  // This method must be passed through immediately.
+  listener.onStartRequest(null);
+  equal(testListener.state, "start", "test listener started");
+
+  const TEST_INPUT = "hi bob";
+
+  const testStream = Cc["@mozilla.org/storagestream;1"].createInstance(
+    Ci.nsIStorageStream
+  );
+  testStream.init(512, 512);
+  const out = testStream.getOutputStream(0);
+  out.write(TEST_INPUT, TEST_INPUT.length);
+  out.close();
+  const testInputStream = testStream.newInputStream(0);
+
+  const activityDistributor = Cc[
+    "@mozilla.org/network/http-activity-distributor;1"
+  ].getService(Ci.nsIHttpActivityDistributor);
+  let activitySeen = false;
+  listener.addActivityCallback(
+    () => {
+      activitySeen = true;
+    },
+    null,
+    null,
+    null,
+    activityDistributor.ACTIVITY_SUBTYPE_RESPONSE_COMPLETE,
+    null,
+    TEST_INPUT.length,
+    null
+  );
+
+  // onDataAvailable is required to immediately read the data.
+  listener.onDataAvailable(null, testInputStream, 0, 6);
+  equal(testInputStream.available(), 0, "no more data should be available");
+  equal(
+    testListener.state,
+    "start",
+    "test listener should not have received data"
+  );
+  equal(activitySeen, false, "activity not distributed yet");
+
+  let newState = await testListener.onStateChanged();
+  equal(newState, "data", "test listener received data");
+  equal(testListener.data, TEST_INPUT, "test listener received all the data");
+  equal(activitySeen, true, "activity has been distributed");
+
+  const onChange = testListener.onStateChanged();
+  listener.onStopRequest(null, null);
+  newState = await onChange;
+  equal(newState, "stop", "onStateChanged reported");
+});
diff --git a/devtools/shared/network-observer/test/xpcshell/xpcshell.ini b/devtools/shared/network-observer/test/xpcshell/xpcshell.ini
new file mode 100644
index 0000000000..3f5c1b674a
--- /dev/null
+++ b/devtools/shared/network-observer/test/xpcshell/xpcshell.ini
@@ -0,0 +1,15 @@
+[DEFAULT]
+tags = devtools
+head = head.js
+firefox-appdir = browser
+skip-if = toolkit == 'android'
+support-files =
+
+[test_network_helper.js]
+[test_security-info-certificate.js]
+[test_security-info-parser.js]
+[test_security-info-protocol-version.js]
+[test_security-info-state.js]
+[test_security-info-static-hpkp.js]
+[test_security-info-weakness-reasons.js]
+[test_throttle.js]