[polymer] Merge of master into polymer10-migration

netlog_viewer/browser_bridge.js

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Populated by constants from the browser.  Used only by this file.
+var NetInfoSources = null;
+
+/**
+ * This class provides a "bridge" for communicating between the javascript and
+ * the browser.
+ */
+var BrowserBridge = (function() {
+  'use strict';
+
+  /**
+   * Delay in milliseconds between updates of certain browser information.
+   */
+  var POLL_INTERVAL_MS = 5000;
+
+  /**
+   * @constructor
+   */
+  function BrowserBridge() {
+    assertFirstConstructorCall(BrowserBridge);
+
+    // List of observers for various bits of browser state.
+    this.connectionTestsObservers_ = [];
+    this.hstsObservers_ = [];
+    this.constantsObservers_ = [];
+    this.crosONCFileParseObservers_ = [];
+    this.storeDebugLogsObservers_ = [];
+    this.setNetworkDebugModeObservers_ = [];
+    // Unprocessed data received before the constants.  This serves to protect
+    // against passing along data before having information on how to interpret
+    // it.
+    this.earlyReceivedData_ = [];
+
+    this.pollableDataHelpers_ = {};
+
+    // Add PollableDataHelpers for NetInfoSources, which retrieve information
+    // directly from the network stack.
+    this.addNetInfoPollableDataHelper('proxySettings',
+                                      'onProxySettingsChanged');
+    this.addNetInfoPollableDataHelper('badProxies', 'onBadProxiesChanged');
+    this.addNetInfoPollableDataHelper('hostResolverInfo',
+                                      'onHostResolverInfoChanged');
+    this.addNetInfoPollableDataHelper('socketPoolInfo',
+                                      'onSocketPoolInfoChanged');
+    this.addNetInfoPollableDataHelper('spdySessionInfo',
+                                      'onSpdySessionInfoChanged');
+    this.addNetInfoPollableDataHelper('spdyStatus', 'onSpdyStatusChanged');
+    this.addNetInfoPollableDataHelper('altSvcMappings',
+                                      'onAltSvcMappingsChanged');
+    this.addNetInfoPollableDataHelper('quicInfo', 'onQuicInfoChanged');
+    this.addNetInfoPollableDataHelper('sdchInfo', 'onSdchInfoChanged');
+    this.addNetInfoPollableDataHelper('httpCacheInfo',
+                                      'onHttpCacheInfoChanged');
+
+    // Add other PollableDataHelpers.
+    this.pollableDataHelpers_.sessionNetworkStats =
+        new PollableDataHelper('onSessionNetworkStatsChanged',
+                               this.sendGetSessionNetworkStats.bind(this));
+    this.pollableDataHelpers_.historicNetworkStats =
+        new PollableDataHelper('onHistoricNetworkStatsChanged',
+                               this.sendGetHistoricNetworkStats.bind(this));
+    if (cr.isWindows) {
+      this.pollableDataHelpers_.serviceProviders =
+          new PollableDataHelper('onServiceProvidersChanged',
+                                 this.sendGetServiceProviders.bind(this));
+    }
+    this.pollableDataHelpers_.prerenderInfo =
+        new PollableDataHelper('onPrerenderInfoChanged',
+                               this.sendGetPrerenderInfo.bind(this));
+    this.pollableDataHelpers_.extensionInfo =
+        new PollableDataHelper('onExtensionInfoChanged',
+                               this.sendGetExtensionInfo.bind(this));
+    this.pollableDataHelpers_.dataReductionProxyInfo =
+        new PollableDataHelper('onDataReductionProxyInfoChanged',
+                               this.sendGetDataReductionProxyInfo.bind(this));
+
+    // Setting this to true will cause messages from the browser to be ignored,
+    // and no messages will be sent to the browser, either.  Intended for use
+    // when viewing log files.
+    this.disabled_ = false;
+
+    // Interval id returned by window.setInterval for polling timer.
+    this.pollIntervalId_ = null;
+  }
+
+  cr.addSingletonGetter(BrowserBridge);
+
+  BrowserBridge.prototype = {
+
+    //--------------------------------------------------------------------------
+    // Messages sent to the browser
+    //--------------------------------------------------------------------------
+
+    /**
+     * Wraps |chrome.send|.  Doesn't send anything when disabled.
+     */
+    send: function(value1, value2) {
+      if (console && console.warn) {
+        console.warn('TODO: Called deprecated BrowserBridge.send');
+      }
+      return;
+
+      /*if (!this.disabled_) {
+        if (arguments.length == 1) {
+          chrome.send(value1);
+        } else if (arguments.length == 2) {
+          chrome.send(value1, value2);
+        } else {
+          throw 'Unsupported number of arguments.';
+        }
+      }*/
+    },
+
+    sendReady: function() {
+      this.send('notifyReady');
+      this.setPollInterval(POLL_INTERVAL_MS);
+    },
+
+    /**
+     * Some of the data we are interested is not currently exposed as a
+     * stream.  This starts polling those with active observers (visible
+     * views) every |intervalMs|.  Subsequent calls override previous calls
+     * to this function.  If |intervalMs| is 0, stops polling.
+     */
+    setPollInterval: function(intervalMs) {
+      if (this.pollIntervalId_ !== null) {
+        window.clearInterval(this.pollIntervalId_);
+        this.pollIntervalId_ = null;
+      }
+
+      if (intervalMs > 0) {
+        this.pollIntervalId_ =
+            window.setInterval(this.checkForUpdatedInfo.bind(this, false),
+                               intervalMs);
+      }
+    },
+
+    sendGetNetInfo: function(netInfoSource) {
+      // If don't have constants yet, don't do anything yet.
+      if (NetInfoSources)
+        this.send('getNetInfo', [NetInfoSources[netInfoSource]]);
+    },
+
+    sendReloadProxySettings: function() {
+      this.send('reloadProxySettings');
+    },
+
+    sendClearBadProxies: function() {
+      this.send('clearBadProxies');
+    },
+
+    sendClearHostResolverCache: function() {
+      this.send('clearHostResolverCache');
+    },
+
+    sendClearBrowserCache: function() {
+      this.send('clearBrowserCache');
+    },
+
+    sendClearAllCache: function() {
+      this.sendClearHostResolverCache();
+      this.sendClearBrowserCache();
+    },
+
+    sendStartConnectionTests: function(url) {
+      this.send('startConnectionTests', [url]);
+    },
+
+    sendHSTSQuery: function(domain) {
+      this.send('hstsQuery', [domain]);
+    },
+
+    sendHSTSAdd: function(domain, sts_include_subdomains,
+                          pkp_include_subdomains, pins) {
+      this.send('hstsAdd', [domain, sts_include_subdomains,
+                            pkp_include_subdomains, pins]);
+    },
+
+    sendHSTSDelete: function(domain) {
+      this.send('hstsDelete', [domain]);
+    },
+
+    sendGetSessionNetworkStats: function() {
+      this.send('getSessionNetworkStats');
+    },
+
+    sendGetHistoricNetworkStats: function() {
+      this.send('getHistoricNetworkStats');
+    },
+
+    sendCloseIdleSockets: function() {
+      this.send('closeIdleSockets');
+    },
+
+    sendFlushSocketPools: function() {
+      this.send('flushSocketPools');
+    },
+
+    sendGetServiceProviders: function() {
+      this.send('getServiceProviders');
+    },
+
+    sendGetPrerenderInfo: function() {
+      this.send('getPrerenderInfo');
+    },
+
+    sendGetExtensionInfo: function() {
+      this.send('getExtensionInfo');
+    },
+
+    sendGetDataReductionProxyInfo: function() {
+      this.send('getDataReductionProxyInfo');
+    },
+
+    setCaptureMode: function(captureMode) {
+      this.send('setCaptureMode', ['' + captureMode]);
+    },
+
+    importONCFile: function(fileContent, passcode) {
+      this.send('importONCFile', [fileContent, passcode]);
+    },
+
+    storeDebugLogs: function() {
+      this.send('storeDebugLogs');
+    },
+
+    setNetworkDebugMode: function(subsystem) {
+      this.send('setNetworkDebugMode', [subsystem]);
+    },
+
+    //--------------------------------------------------------------------------
+    // Messages received from the browser.
+    //--------------------------------------------------------------------------
+
+    receive: function(command, params) {
+      // Does nothing if disabled.
+      if (this.disabled_)
+        return;
+
+      // If no constants have been received, and params does not contain the
+      // constants, delay handling the data.
+      if (Constants == null && command != 'receivedConstants') {
+        this.earlyReceivedData_.push({ command: command, params: params });
+        return;
+      }
+
+      this[command](params);
+
+      // Handle any data that was received early in the order it was received,
+      // once the constants have been processed.
+      if (this.earlyReceivedData_ != null) {
+        for (var i = 0; i < this.earlyReceivedData_.length; i++) {
+          var command = this.earlyReceivedData_[i];
+          this[command.command](command.params);
+        }
+        this.earlyReceivedData_ = null;
+      }
+    },
+
+    receivedConstants: function(constants) {
+      NetInfoSources = constants.netInfoSources;
+      for (var i = 0; i < this.constantsObservers_.length; i++)
+        this.constantsObservers_[i].onReceivedConstants(constants);
+      // May have been waiting for the constants to be received before getting
+      // information for the currently displayed tab.
+      this.checkForUpdatedInfo();
+    },
+
+    receivedLogEntries: function(logEntries) {
+      EventsTracker.getInstance().addLogEntries(logEntries);
+    },
+
+    receivedNetInfo: function(netInfo) {
+      // Dispatch |netInfo| to the various PollableDataHelpers listening to
+      // each field it contains.
+      //
+      // Currently information is only received from one source at a time, but
+      // the API does allow for data from more that one to be requested at once.
+      for (var source in netInfo)
+        this.pollableDataHelpers_[source].update(netInfo[source]);
+    },
+
+    receivedSessionNetworkStats: function(sessionNetworkStats) {
+      this.pollableDataHelpers_.sessionNetworkStats.update(sessionNetworkStats);
+    },
+
+    receivedHistoricNetworkStats: function(historicNetworkStats) {
+      this.pollableDataHelpers_.historicNetworkStats.update(
+          historicNetworkStats);
+    },
+
+    receivedServiceProviders: function(serviceProviders) {
+      this.pollableDataHelpers_.serviceProviders.update(serviceProviders);
+    },
+
+    receivedStartConnectionTestSuite: function() {
+      for (var i = 0; i < this.connectionTestsObservers_.length; i++)
+        this.connectionTestsObservers_[i].onStartedConnectionTestSuite();
+    },
+
+    receivedStartConnectionTestExperiment: function(experiment) {
+      for (var i = 0; i < this.connectionTestsObservers_.length; i++) {
+        this.connectionTestsObservers_[i].onStartedConnectionTestExperiment(
+            experiment);
+      }
+    },
+
+    receivedCompletedConnectionTestExperiment: function(info) {
+      for (var i = 0; i < this.connectionTestsObservers_.length; i++) {
+        this.connectionTestsObservers_[i].onCompletedConnectionTestExperiment(
+            info.experiment, info.result);
+      }
+    },
+
+    receivedCompletedConnectionTestSuite: function() {
+      for (var i = 0; i < this.connectionTestsObservers_.length; i++)
+        this.connectionTestsObservers_[i].onCompletedConnectionTestSuite();
+    },
+
+    receivedHSTSResult: function(info) {
+      for (var i = 0; i < this.hstsObservers_.length; i++)
+        this.hstsObservers_[i].onHSTSQueryResult(info);
+    },
+
+    receivedONCFileParse: function(error) {
+      for (var i = 0; i < this.crosONCFileParseObservers_.length; i++)
+        this.crosONCFileParseObservers_[i].onONCFileParse(error);
+    },
+
+    receivedStoreDebugLogs: function(status) {
+      for (var i = 0; i < this.storeDebugLogsObservers_.length; i++)
+        this.storeDebugLogsObservers_[i].onStoreDebugLogs(status);
+    },
+
+    receivedSetNetworkDebugMode: function(status) {
+      for (var i = 0; i < this.setNetworkDebugModeObservers_.length; i++)
+        this.setNetworkDebugModeObservers_[i].onSetNetworkDebugMode(status);
+    },
+
+    receivedPrerenderInfo: function(prerenderInfo) {
+      this.pollableDataHelpers_.prerenderInfo.update(prerenderInfo);
+    },
+
+    receivedExtensionInfo: function(extensionInfo) {
+      this.pollableDataHelpers_.extensionInfo.update(extensionInfo);
+    },
+
+    receivedDataReductionProxyInfo: function(dataReductionProxyInfo) {
+      this.pollableDataHelpers_.dataReductionProxyInfo.update(
+          dataReductionProxyInfo);
+    },
+
+    //--------------------------------------------------------------------------
+
+    /**
+     * Prevents receiving/sending events to/from the browser.
+     */
+    disable: function() {
+      this.disabled_ = true;
+      this.setPollInterval(0);
+    },
+
+    /**
+     * Returns true if the BrowserBridge has been disabled.
+     */
+    isDisabled: function() {
+      return this.disabled_;
+    },
+
+    /**
+     * Adds a listener of the proxy settings. |observer| will be called back
+     * when data is received, through:
+     *
+     *   observer.onProxySettingsChanged(proxySettings)
+     *
+     * |proxySettings| is a dictionary with (up to) two properties:
+     *
+     *   "original"  -- The settings that chrome was configured to use
+     *                  (i.e. system settings.)
+     *   "effective" -- The "effective" proxy settings that chrome is using.
+     *                  (decides between the manual/automatic modes of the
+     *                  fetched settings).
+     *
+     * Each of these two configurations is formatted as a string, and may be
+     * omitted if not yet initialized.
+     *
+     * If |ignoreWhenUnchanged| is true, data is only sent when it changes.
+     * If it's false, data is sent whenever it's received from the browser.
+     */
+    addProxySettingsObserver: function(observer, ignoreWhenUnchanged) {
+      this.pollableDataHelpers_.proxySettings.addObserver(observer,
+                                                          ignoreWhenUnchanged);
+    },
+
+    /**
+     * Adds a listener of the proxy settings. |observer| will be called back
+     * when data is received, through:
+     *
+     *   observer.onBadProxiesChanged(badProxies)
+     *
+     * |badProxies| is an array, where each entry has the property:
+     *   badProxies[i].proxy_uri: String identify the proxy.
+     *   badProxies[i].bad_until: The time when the proxy stops being considered
+     *                            bad. Note the time is in time ticks.
+     */
+    addBadProxiesObserver: function(observer, ignoreWhenUnchanged) {
+      this.pollableDataHelpers_.badProxies.addObserver(observer,
+                                                       ignoreWhenUnchanged);
+    },
+
+    /**
+     * Adds a listener of the host resolver info. |observer| will be called back
+     * when data is received, through:
+     *
+     *   observer.onHostResolverInfoChanged(hostResolverInfo)
+     */
+    addHostResolverInfoObserver: function(observer, ignoreWhenUnchanged) {
+      this.pollableDataHelpers_.hostResolverInfo.addObserver(
+          observer, ignoreWhenUnchanged);
+    },
+
+    /**
+     * Adds a listener of the socket pool. |observer| will be called back
+     * when data is received, through:
+     *
+     *   observer.onSocketPoolInfoChanged(socketPoolInfo)
+     */
+    addSocketPoolInfoObserver: function(observer, ignoreWhenUnchanged) {
+      this.pollableDataHelpers_.socketPoolInfo.addObserver(observer,
+                                                           ignoreWhenUnchanged);
+    },
+
+    /**
+     * Adds a listener of the network session. |observer| will be called back
+     * when data is received, through:
+     *
+     *   observer.onSessionNetworkStatsChanged(sessionNetworkStats)
+     */
+    addSessionNetworkStatsObserver: function(observer, ignoreWhenUnchanged) {
+      this.pollableDataHelpers_.sessionNetworkStats.addObserver(
+          observer, ignoreWhenUnchanged);
+    },
+
+    /**
+     * Adds a listener of persistent network session data. |observer| will be
+     * called back when data is received, through:
+     *
+     *   observer.onHistoricNetworkStatsChanged(historicNetworkStats)
+     */
+    addHistoricNetworkStatsObserver: function(observer, ignoreWhenUnchanged) {
+      this.pollableDataHelpers_.historicNetworkStats.addObserver(
+          observer, ignoreWhenUnchanged);
+    },
+
+    /**
+     * Adds a listener of the QUIC info. |observer| will be called back
+     * when data is received, through:
+     *
+     *   observer.onQuicInfoChanged(quicInfo)
+     */
+    addQuicInfoObserver: function(observer, ignoreWhenUnchanged) {
+      this.pollableDataHelpers_.quicInfo.addObserver(
+          observer, ignoreWhenUnchanged);
+    },
+
+    /**
+     * Adds a listener of the SPDY info. |observer| will be called back
+     * when data is received, through:
+     *
+     *   observer.onSpdySessionInfoChanged(spdySessionInfo)
+     */
+    addSpdySessionInfoObserver: function(observer, ignoreWhenUnchanged) {
+      this.pollableDataHelpers_.spdySessionInfo.addObserver(
+          observer, ignoreWhenUnchanged);
+    },
+
+    /**
+     * Adds a listener of the SPDY status. |observer| will be called back
+     * when data is received, through:
+     *
+     *   observer.onSpdyStatusChanged(spdyStatus)
+     */
+    addSpdyStatusObserver: function(observer, ignoreWhenUnchanged) {
+      this.pollableDataHelpers_.spdyStatus.addObserver(observer,
+                                                       ignoreWhenUnchanged);
+    },
+
+    /**
+     * Adds a listener of the altSvcMappings. |observer| will be
+     * called back when data is received, through:
+     *
+     *   observer.onAltSvcMappingsChanged(altSvcMappings)
+     */
+    addAltSvcMappingsObserver: function(observer, ignoreWhenUnchanged) {
+      this.pollableDataHelpers_.altSvcMappings.addObserver(
+          observer, ignoreWhenUnchanged);
+    },
+
+    /**
+     * Adds a listener of the service providers info. |observer| will be called
+     * back when data is received, through:
+     *
+     *   observer.onServiceProvidersChanged(serviceProviders)
+     *
+     * Will do nothing if on a platform other than Windows, as service providers
+     * are only present on Windows.
+     */
+    addServiceProvidersObserver: function(observer, ignoreWhenUnchanged) {
+      if (this.pollableDataHelpers_.serviceProviders) {
+        this.pollableDataHelpers_.serviceProviders.addObserver(
+            observer, ignoreWhenUnchanged);
+      }
+    },
+
+    /**
+     * Adds a listener for the progress of the connection tests.
+     * The observer will be called back with:
+     *
+     *   observer.onStartedConnectionTestSuite();
+     *   observer.onStartedConnectionTestExperiment(experiment);
+     *   observer.onCompletedConnectionTestExperiment(experiment, result);
+     *   observer.onCompletedConnectionTestSuite();
+     */
+    addConnectionTestsObserver: function(observer) {
+      this.connectionTestsObservers_.push(observer);
+    },
+
+    /**
+     * Adds a listener for the http cache info results.
+     * The observer will be called back with:
+     *
+     *   observer.onHttpCacheInfoChanged(info);
+     */
+    addHttpCacheInfoObserver: function(observer, ignoreWhenUnchanged) {
+      this.pollableDataHelpers_.httpCacheInfo.addObserver(
+          observer, ignoreWhenUnchanged);
+    },
+
+    /**
+     * Adds a listener for the results of HSTS (HTTPS Strict Transport Security)
+     * queries. The observer will be called back with:
+     *
+     *   observer.onHSTSQueryResult(result);
+     */
+    addHSTSObserver: function(observer) {
+      this.hstsObservers_.push(observer);
+    },
+
+    /**
+     * Adds a listener for ONC file parse status. The observer will be called
+     * back with:
+     *
+     *   observer.onONCFileParse(error);
+     */
+    addCrosONCFileParseObserver: function(observer) {
+      this.crosONCFileParseObservers_.push(observer);
+    },
+
+    /**
+     * Adds a listener for storing log file status. The observer will be called
+     * back with:
+     *
+     *   observer.onStoreDebugLogs(status);
+     */
+    addStoreDebugLogsObserver: function(observer) {
+      this.storeDebugLogsObservers_.push(observer);
+    },
+
+    /**
+     * Adds a listener for network debugging mode status. The observer
+     * will be called back with:
+     *
+     *   observer.onSetNetworkDebugMode(status);
+     */
+    addSetNetworkDebugModeObserver: function(observer) {
+      this.setNetworkDebugModeObservers_.push(observer);
+    },
+
+    /**
+     * Adds a listener for the received constants event. |observer| will be
+     * called back when the constants are received, through:
+     *
+     *   observer.onReceivedConstants(constants);
+     */
+    addConstantsObserver: function(observer) {
+      this.constantsObservers_.push(observer);
+    },
+
+    /**
+     * Adds a listener for updated prerender info events
+     * |observer| will be called back with:
+     *
+     *   observer.onPrerenderInfoChanged(prerenderInfo);
+     */
+    addPrerenderInfoObserver: function(observer, ignoreWhenUnchanged) {
+      this.pollableDataHelpers_.prerenderInfo.addObserver(
+          observer, ignoreWhenUnchanged);
+    },
+
+    /**
+     * Adds a listener of extension information. |observer| will be called
+     * back when data is received, through:
+     *
+     *   observer.onExtensionInfoChanged(extensionInfo)
+     */
+    addExtensionInfoObserver: function(observer, ignoreWhenUnchanged) {
+      this.pollableDataHelpers_.extensionInfo.addObserver(
+          observer, ignoreWhenUnchanged);
+    },
+
+    /**
+     * Adds a listener of the data reduction proxy info. |observer| will be
+     * called back when data is received, through:
+     *
+     *   observer.onDataReductionProxyInfoChanged(dataReductionProxyInfo)
+     */
+    addDataReductionProxyInfoObserver: function(observer, ignoreWhenUnchanged) {
+      this.pollableDataHelpers_.dataReductionProxyInfo.addObserver(
+          observer, ignoreWhenUnchanged);
+    },
+
+    /**
+     * Adds a listener of SDCH information. |observer| will be called
+     * back when data is received, through:
+     *
+     *   observer.onSdchInfoChanged(sdchInfo)
+     */
+    addSdchInfoObserver: function(observer, ignoreWhenUnchanged) {
+      this.pollableDataHelpers_.sdchInfo.addObserver(
+          observer, ignoreWhenUnchanged);
+    },
+
+    /**
+     * If |force| is true, calls all startUpdate functions.  Otherwise, just
+     * runs updates with active observers.
+     */
+    checkForUpdatedInfo: function(force) {
+      for (var name in this.pollableDataHelpers_) {
+        var helper = this.pollableDataHelpers_[name];
+        if (force || helper.hasActiveObserver())
+          helper.startUpdate();
+      }
+    },
+
+    /**
+     * Calls all startUpdate functions and, if |callback| is non-null,
+     * calls it with the results of all updates.
+     */
+    updateAllInfo: function(callback) {
+      if (callback)
+        new UpdateAllObserver(callback, this.pollableDataHelpers_);
+      this.checkForUpdatedInfo(true);
+    },
+
+    /**
+     * Adds a PollableDataHelper that listens to the specified NetInfoSource.
+     */
+    addNetInfoPollableDataHelper: function(sourceName, observerMethodName) {
+      this.pollableDataHelpers_[sourceName] = new PollableDataHelper(
+          observerMethodName, this.sendGetNetInfo.bind(this, sourceName));
+    },
+  };
+
+  /**
+   * This is a helper class used by BrowserBridge, to keep track of:
+   *   - the list of observers interested in some piece of data.
+   *   - the last known value of that piece of data.
+   *   - the name of the callback method to invoke on observers.
+   *   - the update function.
+   * @constructor
+   */
+  function PollableDataHelper(observerMethodName, startUpdateFunction) {
+    this.observerMethodName_ = observerMethodName;
+    this.startUpdate = startUpdateFunction;
+    this.observerInfos_ = [];
+  }
+
+  PollableDataHelper.prototype = {
+    getObserverMethodName: function() {
+      return this.observerMethodName_;
+    },
+
+    isObserver: function(object) {
+      for (var i = 0; i < this.observerInfos_.length; i++) {
+        if (this.observerInfos_[i].observer === object)
+          return true;
+      }
+      return false;
+    },
+
+    /**
+     * If |ignoreWhenUnchanged| is true, we won't send data again until it
+     * changes.
+     */
+    addObserver: function(observer, ignoreWhenUnchanged) {
+      this.observerInfos_.push(new ObserverInfo(observer, ignoreWhenUnchanged));
+    },
+
+    removeObserver: function(observer) {
+      for (var i = 0; i < this.observerInfos_.length; i++) {
+        if (this.observerInfos_[i].observer === observer) {
+          this.observerInfos_.splice(i, 1);
+          return;
+        }
+      }
+    },
+
+    /**
+     * Helper function to handle calling all the observers, but ONLY if the data
+     * has actually changed since last time or the observer has yet to receive
+     * any data. This is used for data we received from browser on an update
+     * loop.
+     */
+    update: function(data) {
+      var prevData = this.currentData_;
+      var changed = false;
+
+      // If the data hasn't changed since last time, will only need to notify
+      // observers that have not yet received any data.
+      if (!prevData || JSON.stringify(prevData) != JSON.stringify(data)) {
+        changed = true;
+        this.currentData_ = data;
+      }
+
+      // Notify the observers of the change, as needed.
+      for (var i = 0; i < this.observerInfos_.length; i++) {
+        var observerInfo = this.observerInfos_[i];
+        if (changed || !observerInfo.hasReceivedData ||
+            !observerInfo.ignoreWhenUnchanged) {
+          observerInfo.observer[this.observerMethodName_](this.currentData_);
+          observerInfo.hasReceivedData = true;
+        }
+      }
+    },
+
+    /**
+     * Returns true if one of the observers actively wants the data
+     * (i.e. is visible).
+     */
+    hasActiveObserver: function() {
+      for (var i = 0; i < this.observerInfos_.length; i++) {
+        if (this.observerInfos_[i].observer.isActive())
+          return true;
+      }
+      return false;
+    }
+  };
+
+  /**
+   * This is a helper class used by PollableDataHelper, to keep track of
+   * each observer and whether or not it has received any data.  The
+   * latter is used to make sure that new observers get sent data on the
+   * update following their creation.
+   * @constructor
+   */
+  function ObserverInfo(observer, ignoreWhenUnchanged) {
+    this.observer = observer;
+    this.hasReceivedData = false;
+    this.ignoreWhenUnchanged = ignoreWhenUnchanged;
+  }
+
+  /**
+   * This is a helper class used by BrowserBridge to send data to
+   * a callback once data from all polls has been received.
+   *
+   * It works by keeping track of how many polling functions have
+   * yet to receive data, and recording the data as it it received.
+   *
+   * @constructor
+   */
+  function UpdateAllObserver(callback, pollableDataHelpers) {
+    this.callback_ = callback;
+    this.observingCount_ = 0;
+    this.updatedData_ = {};
+
+    for (var name in pollableDataHelpers) {
+      ++this.observingCount_;
+      var helper = pollableDataHelpers[name];
+      helper.addObserver(this);
+      this[helper.getObserverMethodName()] =
+          this.onDataReceived_.bind(this, helper, name);
+    }
+  }
+
+  UpdateAllObserver.prototype = {
+    isActive: function() {
+      return true;
+    },
+
+    onDataReceived_: function(helper, name, data) {
+      helper.removeObserver(this);
+      --this.observingCount_;
+      this.updatedData_[name] = data;
+      if (this.observingCount_ == 0)
+        this.callback_(this.updatedData_);
+    }
+  };
+
+  return BrowserBridge;
+})();
+