/* 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/. */ "use strict"; this.EXPORTED_SYMBOLS = ["PageThumbs", "PageThumbsStorage"]; const Cu = Components.utils; const Cc = Components.classes; const Ci = Components.interfaces; const HTML_NAMESPACE = "http://www.w3.org/1999/xhtml"; const PREF_STORAGE_VERSION = "browser.pagethumbnails.storage_version"; const LATEST_STORAGE_VERSION = 3; const EXPIRATION_MIN_CHUNK_SIZE = 50; const EXPIRATION_INTERVAL_SECS = 3600; // If a request for a thumbnail comes in and we find one that is "stale" // (or don't find one at all) we automatically queue a request to generate a // new one. const MAX_THUMBNAIL_AGE_SECS = 172800; // 2 days == 60*60*24*2 == 172800 secs. /** * Name of the directory in the profile that contains the thumbnails. */ const THUMBNAIL_DIRECTORY = "thumbnails"; /** * The default background color for page thumbnails. */ const THUMBNAIL_BG_COLOR = "#fff"; Cu.import("resource://gre/modules/XPCOMUtils.jsm", this); Cu.import("resource://gre/modules/osfile/_PromiseWorker.jsm", this); Cu.import("resource://gre/modules/commonjs/sdk/core/promise.js", this); Cu.import("resource://gre/modules/osfile.jsm", this); XPCOMUtils.defineLazyModuleGetter(this, "NetUtil", "resource://gre/modules/NetUtil.jsm"); XPCOMUtils.defineLazyModuleGetter(this, "Services", "resource://gre/modules/Services.jsm"); XPCOMUtils.defineLazyModuleGetter(this, "FileUtils", "resource://gre/modules/FileUtils.jsm"); XPCOMUtils.defineLazyModuleGetter(this, "PlacesUtils", "resource://gre/modules/PlacesUtils.jsm"); XPCOMUtils.defineLazyServiceGetter(this, "gUpdateTimerManager", "@mozilla.org/updates/timer-manager;1", "nsIUpdateTimerManager"); XPCOMUtils.defineLazyGetter(this, "gCryptoHash", function () { return Cc["@mozilla.org/security/hash;1"].createInstance(Ci.nsICryptoHash); }); XPCOMUtils.defineLazyGetter(this, "gUnicodeConverter", function () { let converter = Cc["@mozilla.org/intl/scriptableunicodeconverter"] .createInstance(Ci.nsIScriptableUnicodeConverter); converter.charset = 'utf8'; return converter; }); XPCOMUtils.defineLazyModuleGetter(this, "Task", "resource://gre/modules/Task.jsm"); XPCOMUtils.defineLazyModuleGetter(this, "Deprecated", "resource://gre/modules/Deprecated.jsm"); /** * Utilities for dealing with promises and Task.jsm */ const TaskUtils = { /** * Add logging to a promise. * * @param {Promise} promise * @return {Promise} A promise behaving as |promise|, but with additional * logging in case of uncaught error. */ captureErrors: function captureErrors(promise) { return promise.then( null, function onError(reason) { Cu.reportError("Uncaught asynchronous error: " + reason + " at\n" + reason.stack + "\n"); throw reason; } ); }, /** * Spawn a new Task from a generator. * * This function behaves as |Task.spawn|, with the exception that it * adds logging in case of uncaught error. For more information, see * the documentation of |Task.jsm|. * * @param {generator} gen Some generator. * @return {Promise} A promise built from |gen|, with the same semantics * as |Task.spawn(gen)|. */ spawn: function spawn(gen) { return this.captureErrors(Task.spawn(gen)); }, /** * Read the bytes from a blob, asynchronously. * * @return {Promise} * @resolve {ArrayBuffer} In case of success, the bytes contained in the blob. * @reject {DOMError} In case of error, the underlying DOMError. */ readBlob: function readBlob(blob) { let deferred = Promise.defer(); let reader = Cc["@mozilla.org/files/filereader;1"].createInstance(Ci.nsIDOMFileReader); reader.onloadend = function onloadend() { if (reader.readyState != Ci.nsIDOMFileReader.DONE) { deferred.reject(reader.error); } else { deferred.resolve(reader.result); } }; reader.readAsArrayBuffer(blob); return deferred.promise; } }; /** * Singleton providing functionality for capturing web page thumbnails and for * accessing them if already cached. */ this.PageThumbs = { _initialized: false, /** * The calculated width and height of the thumbnails. */ _thumbnailWidth : 0, _thumbnailHeight : 0, /** * The scheme to use for thumbnail urls. */ get scheme() "moz-page-thumb", /** * The static host to use for thumbnail urls. */ get staticHost() "thumbnail", /** * The thumbnails' image type. */ get contentType() "image/png", init: function PageThumbs_init() { if (!this._initialized) { this._initialized = true; PlacesUtils.history.addObserver(PageThumbsHistoryObserver, false); // Migrate the underlying storage, if needed. PageThumbsStorageMigrator.migrate(); PageThumbsExpiration.init(); } }, uninit: function PageThumbs_uninit() { if (this._initialized) { this._initialized = false; PlacesUtils.history.removeObserver(PageThumbsHistoryObserver); } }, /** * Gets the thumbnail image's url for a given web page's url. * @param aUrl The web page's url that is depicted in the thumbnail. * @return The thumbnail image's url. */ getThumbnailURL: function PageThumbs_getThumbnailURL(aUrl) { return this.scheme + "://" + this.staticHost + "?url=" + encodeURIComponent(aUrl); }, /** * Gets the path of the thumbnail file for a given web page's * url. This file may or may not exist depending on whether the * thumbnail has been captured or not. * * @param aUrl The web page's url. * @return The path of the thumbnail file. */ getThumbnailPath: function PageThumbs_getThumbnailPath(aUrl) { return PageThumbsStorage.getFilePathForURL(aUrl); }, /** * Captures a thumbnail for the given window. * @param aWindow The DOM window to capture a thumbnail from. * @param aCallback The function to be called when the thumbnail has been * captured. The first argument will be the data stream * containing the image data. */ capture: function PageThumbs_capture(aWindow, aCallback) { if (!this._prefEnabled()) { return; } let canvas = this._createCanvas(); this.captureToCanvas(aWindow, canvas); // Fetch the canvas data on the next event loop tick so that we allow // some event processing in between drawing to the canvas and encoding // its data. We want to block the UI as short as possible. See bug 744100. Services.tm.currentThread.dispatch(function () { canvas.mozFetchAsStream(aCallback, this.contentType); }.bind(this), Ci.nsIThread.DISPATCH_NORMAL); }, /** * Captures a thumbnail for the given window. * * @param aWindow The DOM window to capture a thumbnail from. * @return {Promise} * @resolve {Blob} The thumbnail, as a Blob. */ captureToBlob: function PageThumbs_captureToBlob(aWindow) { if (!this._prefEnabled()) { return null; } let canvas = this._createCanvas(); this.captureToCanvas(aWindow, canvas); let deferred = Promise.defer(); let type = this.contentType; // Fetch the canvas data on the next event loop tick so that we allow // some event processing in between drawing to the canvas and encoding // its data. We want to block the UI as short as possible. See bug 744100. canvas.toBlob(function asBlob(blob) { deferred.resolve(blob, type); }); return deferred.promise; }, /** * Captures a thumbnail from a given window and draws it to the given canvas. * @param aWindow The DOM window to capture a thumbnail from. * @param aCanvas The canvas to draw to. */ captureToCanvas: function PageThumbs_captureToCanvas(aWindow, aCanvas) { let telemetryCaptureTime = new Date(); this._captureToCanvas(aWindow, aCanvas); let telemetry = Services.telemetry; telemetry.getHistogramById("FX_THUMBNAILS_CAPTURE_TIME_MS") .add(new Date() - telemetryCaptureTime); }, // The background thumbnail service captures to canvas but doesn't want to // participate in this service's telemetry, which is why this method exists. _captureToCanvas: function PageThumbs__captureToCanvas(aWindow, aCanvas) { let [sw, sh, scale] = this._determineCropSize(aWindow, aCanvas); let ctx = aCanvas.getContext("2d"); // Scale the canvas accordingly. ctx.save(); ctx.scale(scale, scale); try { // Draw the window contents to the canvas. ctx.drawWindow(aWindow, 0, 0, sw, sh, THUMBNAIL_BG_COLOR, ctx.DRAWWINDOW_DO_NOT_FLUSH); } catch (e) { // We couldn't draw to the canvas for some reason. } ctx.restore(); }, /** * Captures a thumbnail for the given browser and stores it to the cache. * @param aBrowser The browser to capture a thumbnail for. * @param aCallback The function to be called when finished (optional). */ captureAndStore: function PageThumbs_captureAndStore(aBrowser, aCallback) { if (!this._prefEnabled()) { return; } let url = aBrowser.currentURI.spec; let channel = aBrowser.docShell.currentDocumentChannel; let originalURL = channel.originalURI.spec; // see if this was an error response. let wasError = this._isChannelErrorResponse(channel); TaskUtils.spawn((function task() { let isSuccess = true; try { let blob = yield this.captureToBlob(aBrowser.contentWindow); let buffer = yield TaskUtils.readBlob(blob); yield this._store(originalURL, url, buffer, wasError); } catch (_) { isSuccess = false; } if (aCallback) { aCallback(isSuccess); } }).bind(this)); }, /** * Checks if an existing thumbnail for the specified URL is either missing * or stale, and if so, captures and stores it. Once the thumbnail is stored, * an observer service notification will be sent, so consumers should observe * such notifications if they want to be notified of an updated thumbnail. * * @param aBrowser The content window of this browser will be captured. * @param aCallback The function to be called when finished (optional). */ captureAndStoreIfStale: function PageThumbs_captureAndStoreIfStale(aBrowser, aCallback) { let url = aBrowser.currentURI.spec; PageThumbsStorage.isFileRecentForURL(url).then(recent => { if (!recent.ok && // Careful, the call to PageThumbsStorage is async, so the browser may // have navigated away from the URL or even closed. aBrowser.currentURI && aBrowser.currentURI.spec == url) { this.captureAndStore(aBrowser, aCallback); } else if (aCallback) { aCallback(true); } }, err => { if (aCallback) aCallback(false); }); }, /** * Stores data to disk for the given URLs. * * NB: The background thumbnail service calls this, too. * * @param aOriginalURL The URL with which the capture was initiated. * @param aFinalURL The URL to which aOriginalURL ultimately resolved. * @param aData An ArrayBuffer containing the image data. * @param aNoOverwrite If true and files for the URLs already exist, the files * will not be overwritten. * @return {Promise} */ _store: function PageThumbs__store(aOriginalURL, aFinalURL, aData, aNoOverwrite) { return TaskUtils.spawn(function () { let telemetryStoreTime = new Date(); yield PageThumbsStorage.writeData(aFinalURL, aData, aNoOverwrite); Services.telemetry.getHistogramById("FX_THUMBNAILS_STORE_TIME_MS") .add(new Date() - telemetryStoreTime); Services.obs.notifyObservers(null, "page-thumbnail:create", aFinalURL); // We've been redirected. Create a copy of the current thumbnail for // the redirect source. We need to do this because: // // 1) Users can drag any kind of links onto the newtab page. If those // links redirect to a different URL then we want to be able to // provide thumbnails for both of them. // // 2) The newtab page should actually display redirect targets, only. // Because of bug 559175 this information can get lost when using // Sync and therefore also redirect sources appear on the newtab // page. We also want thumbnails for those. if (aFinalURL != aOriginalURL) { yield PageThumbsStorage.copy(aFinalURL, aOriginalURL, aNoOverwrite); Services.obs.notifyObservers(null, "page-thumbnail:create", aOriginalURL); } }); }, /** * Register an expiration filter. * * When thumbnails are going to expire, each registered filter is asked for a * list of thumbnails to keep. * * The filter (if it is a callable) or its filterForThumbnailExpiration method * (if the filter is an object) is called with a single argument. The * argument is a callback function. The filter must call the callback * function and pass it an array of zero or more URLs. (It may do so * asynchronously.) Thumbnails for those URLs will be except from expiration. * * @param aFilter callable, or object with filterForThumbnailExpiration method */ addExpirationFilter: function PageThumbs_addExpirationFilter(aFilter) { PageThumbsExpiration.addFilter(aFilter); }, /** * Unregister an expiration filter. * @param aFilter A filter that was previously passed to addExpirationFilter. */ removeExpirationFilter: function PageThumbs_removeExpirationFilter(aFilter) { PageThumbsExpiration.removeFilter(aFilter); }, /** * Determines the crop size for a given content window. * @param aWindow The content window. * @param aCanvas The target canvas. * @return An array containing width, height and scale. */ _determineCropSize: function PageThumbs_determineCropSize(aWindow, aCanvas) { let utils = aWindow.QueryInterface(Ci.nsIInterfaceRequestor) .getInterface(Ci.nsIDOMWindowUtils); let sbWidth = {}, sbHeight = {}; try { utils.getScrollbarSize(false, sbWidth, sbHeight); } catch (e) { // This might fail if the window does not have a presShell. Cu.reportError("Unable to get scrollbar size in _determineCropSize."); sbWidth.value = sbHeight.value = 0; } // Even in RTL mode, scrollbars are always on the right. // So there's no need to determine a left offset. let sw = aWindow.innerWidth - sbWidth.value; let sh = aWindow.innerHeight - sbHeight.value; let {width: thumbnailWidth, height: thumbnailHeight} = aCanvas; let scale = Math.min(Math.max(thumbnailWidth / sw, thumbnailHeight / sh), 1); let scaledWidth = sw * scale; let scaledHeight = sh * scale; if (scaledHeight > thumbnailHeight) sh -= Math.floor(Math.abs(scaledHeight - thumbnailHeight) * scale); if (scaledWidth > thumbnailWidth) sw -= Math.floor(Math.abs(scaledWidth - thumbnailWidth) * scale); return [sw, sh, scale]; }, /** * Creates a new hidden canvas element. * @param aWindow The document of this window will be used to create the * canvas. If not given, the hidden window will be used. * @return The newly created canvas. */ _createCanvas: function PageThumbs_createCanvas(aWindow) { let doc = (aWindow || Services.appShell.hiddenDOMWindow).document; let canvas = doc.createElementNS(HTML_NAMESPACE, "canvas"); canvas.mozOpaque = true; canvas.mozImageSmoothingEnabled = true; let [thumbnailWidth, thumbnailHeight] = this._getThumbnailSize(); canvas.width = thumbnailWidth; canvas.height = thumbnailHeight; return canvas; }, /** * Calculates the thumbnail size based on current desktop's dimensions. * @return The calculated thumbnail size or a default if unable to calculate. */ _getThumbnailSize: function PageThumbs_getThumbnailSize() { if (!this._thumbnailWidth || !this._thumbnailHeight) { let screenManager = Cc["@mozilla.org/gfx/screenmanager;1"] .getService(Ci.nsIScreenManager); let left = {}, top = {}, width = {}, height = {}; screenManager.primaryScreen.GetRectDisplayPix(left, top, width, height); this._thumbnailWidth = Math.round(width.value / 3); this._thumbnailHeight = Math.round(height.value / 3); } return [this._thumbnailWidth, this._thumbnailHeight]; }, /** * Given a channel, returns true if it should be considered an "error * response", false otherwise. */ _isChannelErrorResponse: function(channel) { // No valid document channel sounds like an error to me! if (!channel) return true; if (!(channel instanceof Ci.nsIHttpChannel)) // it might be FTP etc, so assume it's ok. return false; try { return !channel.requestSucceeded; } catch (_) { // not being able to determine success is surely failure! return true; } }, _prefEnabled: function PageThumbs_prefEnabled() { try { return !Services.prefs.getBoolPref("browser.pagethumbnails.capturing_disabled"); } catch (e) { return true; } }, }; this.PageThumbsStorage = { // The path for the storage _path: null, get path() { if (!this._path) { this._path = OS.Path.join(OS.Constants.Path.localProfileDir, THUMBNAIL_DIRECTORY); } return this._path; }, ensurePath: function Storage_ensurePath() { // Create the directory (ignore any error if the directory // already exists). As all writes are done from the PageThumbsWorker // thread, which serializes its operations, this ensures that // future operations can proceed without having to check whether // the directory exists. return PageThumbsWorker.post("makeDir", [this.path, {ignoreExisting: true}]).then( null, function onError(aReason) { Components.utils.reportError("Could not create thumbnails directory" + aReason); }); }, getLeafNameForURL: function Storage_getLeafNameForURL(aURL) { if (typeof aURL != "string") { throw new TypeError("Expecting a string"); } let hash = this._calculateMD5Hash(aURL); return hash + ".png"; }, getFilePathForURL: function Storage_getFilePathForURL(aURL) { return OS.Path.join(this.path, this.getLeafNameForURL(aURL)); }, /** * Write the contents of a thumbnail, off the main thread. * * @param {string} aURL The url for which to store a thumbnail. * @param {ArrayBuffer} aData The data to store in the thumbnail, as * an ArrayBuffer. This array buffer is neutered and cannot be * reused after the copy. * @param {boolean} aNoOverwrite If true and the thumbnail's file already * exists, the file will not be overwritten. * * @return {Promise} */ writeData: function Storage_writeData(aURL, aData, aNoOverwrite) { let path = this.getFilePathForURL(aURL); this.ensurePath(); aData = new Uint8Array(aData); let msg = [ path, aData, { tmpPath: path + ".tmp", bytes: aData.byteLength, noOverwrite: aNoOverwrite, flush: false /*thumbnails do not require the level of guarantee provided by flush*/ }]; return PageThumbsWorker.post("writeAtomic", msg, msg /*we don't want that message garbage-collected, as OS.Shared.Type.void_t.in_ptr.toMsg uses C-level memory tricks to enforce zero-copy*/). then(null, this._eatNoOverwriteError(aNoOverwrite)); }, /** * Copy a thumbnail, off the main thread. * * @param {string} aSourceURL The url of the thumbnail to copy. * @param {string} aTargetURL The url of the target thumbnail. * @param {boolean} aNoOverwrite If true and the target file already exists, * the file will not be overwritten. * * @return {Promise} */ copy: function Storage_copy(aSourceURL, aTargetURL, aNoOverwrite) { this.ensurePath(); let sourceFile = this.getFilePathForURL(aSourceURL); let targetFile = this.getFilePathForURL(aTargetURL); let options = { noOverwrite: aNoOverwrite }; return PageThumbsWorker.post("copy", [sourceFile, targetFile, options]). then(null, this._eatNoOverwriteError(aNoOverwrite)); }, /** * Remove a single thumbnail, off the main thread. * * @return {Promise} */ remove: function Storage_remove(aURL) { return PageThumbsWorker.post("remove", [this.getFilePathForURL(aURL)]); }, /** * Remove all thumbnails, off the main thread. * * @return {Promise} */ wipe: function Storage_wipe() { return PageThumbsWorker.post("wipe", [this.path]); }, fileExistsForURL: function Storage_fileExistsForURL(aURL) { return PageThumbsWorker.post("exists", [this.getFilePathForURL(aURL)]); }, isFileRecentForURL: function Storage_isFileRecentForURL(aURL) { return PageThumbsWorker.post("isFileRecent", [this.getFilePathForURL(aURL), MAX_THUMBNAIL_AGE_SECS]); }, _calculateMD5Hash: function Storage_calculateMD5Hash(aValue) { let hash = gCryptoHash; let value = gUnicodeConverter.convertToByteArray(aValue); hash.init(hash.MD5); hash.update(value, value.length); return this._convertToHexString(hash.finish(false)); }, _convertToHexString: function Storage_convertToHexString(aData) { let hex = ""; for (let i = 0; i < aData.length; i++) hex += ("0" + aData.charCodeAt(i).toString(16)).slice(-2); return hex; }, /** * For functions that take a noOverwrite option, OS.File throws an error if * the target file exists and noOverwrite is true. We don't consider that an * error, and we don't want such errors propagated. * * @param {aNoOverwrite} The noOverwrite option used in the OS.File operation. * * @return {function} A function that should be passed as the second argument * to then() (the `onError` argument). */ _eatNoOverwriteError: function Storage__eatNoOverwriteError(aNoOverwrite) { return function onError(err) { if (!aNoOverwrite || !(err instanceof OS.File.Error) || !err.becauseExists) { throw err; } }; }, // Deprecated, please do not use getFileForURL: function Storage_getFileForURL_DEPRECATED(aURL) { Deprecated.warning("PageThumbs.getFileForURL is deprecated. Please use PageThumbs.getFilePathForURL and OS.File", "https://developer.mozilla.org/docs/JavaScript_OS.File"); // Note: Once this method has been removed, we can get rid of the dependency towards FileUtils return new FileUtils.File(PageThumbsStorage.getFilePathForURL(aURL)); } }; let PageThumbsStorageMigrator = { get currentVersion() { try { return Services.prefs.getIntPref(PREF_STORAGE_VERSION); } catch (e) { // The pref doesn't exist, yet. Return version 0. return 0; } }, set currentVersion(aVersion) { Services.prefs.setIntPref(PREF_STORAGE_VERSION, aVersion); }, migrate: function Migrator_migrate() { let version = this.currentVersion; // Storage version 1 never made it to beta. // At the time of writing only Windows had (ProfD != ProfLD) and we // needed to move thumbnails from the roaming profile to the locale // one so that they're not needlessly included in backups and/or // written via SMB. // Storage version 2 also never made it to beta. // The thumbnail folder structure has been changed and old thumbnails // were not migrated. Instead, we just renamed the current folder to // "-old" and will remove it later. if (version < 3) { this.migrateToVersion3(); } this.currentVersion = LATEST_STORAGE_VERSION; }, /** * Bug 239254 added support for having the disk cache and thumbnail * directories on a local path (i.e. ~/.cache/) under Linux. We'll first * try to move the old thumbnails to their new location. If that's not * possible (because ProfD might be on a different file system than * ProfLD) we'll just discard them. * * @param {string*} local The path to the local profile directory. * Used for testing. Default argument is good for all non-testing uses. * @param {string*} roaming The path to the roaming profile directory. * Used for testing. Default argument is good for all non-testing uses. */ migrateToVersion3: function Migrator_migrateToVersion3( local = OS.Constants.Path.localProfileDir, roaming = OS.Constants.Path.profileDir) { PageThumbsWorker.post( "moveOrDeleteAllThumbnails", [OS.Path.join(roaming, THUMBNAIL_DIRECTORY), OS.Path.join(local, THUMBNAIL_DIRECTORY)] ); } }; let PageThumbsExpiration = { _filters: [], init: function Expiration_init() { gUpdateTimerManager.registerTimer("browser-cleanup-thumbnails", this, EXPIRATION_INTERVAL_SECS); }, addFilter: function Expiration_addFilter(aFilter) { this._filters.push(aFilter); }, removeFilter: function Expiration_removeFilter(aFilter) { let index = this._filters.indexOf(aFilter); if (index > -1) this._filters.splice(index, 1); }, notify: function Expiration_notify(aTimer) { let urls = []; let filtersToWaitFor = this._filters.length; let expire = function expire() { this.expireThumbnails(urls); }.bind(this); // No registered filters. if (!filtersToWaitFor) { expire(); return; } function filterCallback(aURLs) { urls = urls.concat(aURLs); if (--filtersToWaitFor == 0) expire(); } for (let filter of this._filters) { if (typeof filter == "function") filter(filterCallback) else filter.filterForThumbnailExpiration(filterCallback); } }, expireThumbnails: function Expiration_expireThumbnails(aURLsToKeep) { let path = this.path; let keep = [PageThumbsStorage.getLeafNameForURL(url) for (url of aURLsToKeep)]; let msg = [ PageThumbsStorage.path, keep, EXPIRATION_MIN_CHUNK_SIZE ]; return PageThumbsWorker.post( "expireFilesInDirectory", msg ); } }; /** * Interface to a dedicated thread handling I/O */ let PageThumbsWorker = (function() { let worker = new PromiseWorker("resource://gre/modules/PageThumbsWorker.js", OS.Shared.LOG.bind("PageThumbs")); return { post: function post(...args) { let promise = worker.post.apply(worker, args); return promise.then( null, function onError(error) { // Decode any serialized error if (error instanceof PromiseWorker.WorkerError) { throw OS.File.Error.fromMsg(error.data); } else { throw error; } } ); } }; })(); let PageThumbsHistoryObserver = { onDeleteURI: function Thumbnails_onDeleteURI(aURI, aGUID) { PageThumbsStorage.remove(aURI.spec); }, onClearHistory: function Thumbnails_onClearHistory() { PageThumbsStorage.wipe(); }, onTitleChanged: function () {}, onBeginUpdateBatch: function () {}, onEndUpdateBatch: function () {}, onVisit: function () {}, onPageChanged: function () {}, onDeleteVisits: function () {}, QueryInterface: XPCOMUtils.generateQI([Ci.nsINavHistoryObserver]) };