Separate host desktop related functionality into remoting.HostDesktop

remoting.ClientPluginImpl has grown organically over the years and become
a dumping ground of all functionality related to the plugin.

This CL moves all  host desktop related implementation from
remoting.ClientPluginImpl into remoting.ClientPlugin.HostDesktopImpl.

BUG=457890
NOTRY=true
TEST=Unit test passed locally and manually verified ShrinkToFit, bumpScrolling and resizeToClient works

Review URL: https://codereview.chromium.org/929323003

Cr-Commit-Position: refs/heads/master@{#317187}

remoting/remoting_webapp_files.gypi

@@ -119,6 +119,7 @@
     'remoting_webapp_js_client_files': [
       'webapp/crd/js/client_plugin.js',
       'webapp/crd/js/client_plugin_impl.js',
+      'webapp/crd/js/client_plugin_host_desktop_impl.js',
       # TODO(garykac) For client_screen:
       # * Split out pin/access code stuff into separate file.
       # * Move client logic into session_connector
@@ -127,6 +128,7 @@
       'webapp/crd/js/clipboard.js',
       'webapp/crd/js/desktop_connected_view.js',
       'webapp/crd/js/hangout_session.js',
+      'webapp/crd/js/host_desktop.js',
       'webapp/crd/js/session_connector.js',
       'webapp/crd/js/session_connector_impl.js',
       'webapp/crd/js/smart_reconnector.js',

remoting/webapp/browser_test/mock_client_plugin.js

@@ -22,11 +22,10 @@ remoting.MockClientPlugin = function(container) {
   this.container_ = container;
   this.element_ = document.createElement('div');
   this.element_.style.backgroundImage = 'linear-gradient(45deg, blue, red)';
-  this.width_ = 640;
-  this.height_ = 480;
   this.connectionStatusUpdateHandler_ = null;
   this.desktopSizeUpdateHandler_ = null;
   this.container_.appendChild(this.element_);
+  this.hostDesktop_ = new remoting.MockClientPlugin.HostDesktop();
 };
 
 remoting.MockClientPlugin.prototype.dispose = function() {
@@ -35,20 +34,8 @@ remoting.MockClientPlugin.prototype.dispose = function() {
   this.connectionStatusUpdateHandler_ = null;
 };
 
-remoting.MockClientPlugin.prototype.getDesktopWidth = function() {
-  return this.width_;
-};
-
-remoting.MockClientPlugin.prototype.getDesktopHeight = function() {
-  return this.height_;
-};
-
-remoting.MockClientPlugin.prototype.getDesktopXDpi = function() {
-  return 96;
-};
-
-remoting.MockClientPlugin.prototype.getDesktopYDpi = function() {
-  return 96;
+remoting.MockClientPlugin.prototype.hostDesktop = function() {
+  return this.hostDesktop_;
 };
 
 remoting.MockClientPlugin.prototype.element = function() {
@@ -79,15 +66,6 @@ remoting.MockClientPlugin.prototype.remapKey = function(from, to) {};
 
 remoting.MockClientPlugin.prototype.releaseAllKeys = function() {};
 
-remoting.MockClientPlugin.prototype.notifyClientResolution =
-    function(width, height, dpi) {
-  this.width_ = width;
-  this.height_ = height;
-  if (this.desktopSizeUpdateHandler_) {
-    window.setTimeout(this.desktopSizeUpdateHandler_, 0);
-  }
-};
-
 remoting.MockClientPlugin.prototype.onIncomingIq = function(iq) {};
 
 remoting.MockClientPlugin.prototype.isSupportedVersion = function() {
@@ -152,11 +130,6 @@ remoting.MockClientPlugin.prototype.setRouteChangedHandler =
 remoting.MockClientPlugin.prototype.setConnectionReadyHandler =
     function(handler) {};
 
-remoting.MockClientPlugin.prototype.setDesktopSizeUpdateHandler =
-    function(handler) {
-  this.desktopSizeUpdateHandler_ = handler;
-};
-
 remoting.MockClientPlugin.prototype.setCapabilitiesHandler =
     function(handler) {};
 
@@ -175,6 +148,61 @@ remoting.MockClientPlugin.prototype.setFetchThirdPartyTokenHandler =
 remoting.MockClientPlugin.prototype.setFetchPinHandler =
     function(handler) {};
 
+/**
+ * @constructor
+ * @implements {remoting.HostDesktop}
+ * @extends {base.EventSourceImpl}
+ */
+remoting.MockClientPlugin.HostDesktop = function() {
+  /** @private */
+  this.width_ = 0;
+  /** @private */
+  this.height_ = 0;
+  /** @private */
+  this.xDpi_ = 96;
+  /** @private */
+  this.yDpi_ = 96;
+  /** @private */
+  this.resizable_ = true;
+  this.defineEvents(base.values(remoting.HostDesktop.Events));
+};
+base.extend(remoting.MockClientPlugin.HostDesktop, base.EventSourceImpl);
+
+/**
+ * @return {{width:number, height:number, xDpi:number, yDpi:number}}
+ * @override
+ */
+remoting.MockClientPlugin.HostDesktop.prototype.getDimensions = function() {
+  return {
+    width: this.width_,
+    height: this.height_,
+    xDpi: this.xDpi_,
+    yDpi: this.yDpi_
+  };
+};
+
+/**
+ * @return {boolean}
+ * @override
+ */
+remoting.MockClientPlugin.HostDesktop.prototype.isResizable = function() {
+  return this.resizable_;
+};
+
+/**
+ * @param {number} width
+ * @param {number} height
+ * @param {number} deviceScale
+ * @override
+ */
+remoting.MockClientPlugin.HostDesktop.prototype.resize =
+    function(width, height, deviceScale) {
+  this.width_ = width;
+  this.height_ = height;
+  this.xDpi_ = this.yDpi_ = Math.floor(deviceScale * 96);
+  this.raiseEvent(remoting.HostDesktop.Events.sizeChanged,
+                  this.getDimensions());
+};
 
 /**
  * @constructor

remoting/webapp/crd/js/client_plugin.js

@@ -19,24 +19,9 @@ var remoting = remoting || {};
 remoting.ClientPlugin = function() {};
 
 /**
- * @return {number} The width of the remote desktop, in pixels.
+ * @return {remoting.HostDesktop}
  */
-remoting.ClientPlugin.prototype.getDesktopWidth = function() {};
-
-/**
- * @return {number} The height of the remote desktop, in pixels.
- */
-remoting.ClientPlugin.prototype.getDesktopHeight = function() {};
-
-/**
- * @return {number} The x-DPI of the remote desktop.
- */
-remoting.ClientPlugin.prototype.getDesktopXDpi = function() {};
-
-/**
- * @return {number} The y-DPI of the remote desktop.
- */
-remoting.ClientPlugin.prototype.getDesktopYDpi = function() {};
+remoting.ClientPlugin.prototype.hostDesktop = function() {};
 
 /**
  * @return {HTMLElement} The DOM element representing the remote session.
@@ -87,14 +72,6 @@ remoting.ClientPlugin.prototype.remapKey = function(from, to) {};
  */
 remoting.ClientPlugin.prototype.releaseAllKeys = function() {};
 
-/**
- * @param {number} width
- * @param {number} height
- * @param {number} dpi
- */
-remoting.ClientPlugin.prototype.notifyClientResolution =
-    function(width, height, dpi) {};
-
 /**
  * @param {string} iq
  */
@@ -107,7 +84,7 @@ remoting.ClientPlugin.prototype.isSupportedVersion = function() {};
 
 /**
  * @param {remoting.ClientPlugin.Feature} feature
- * @return {boolean} True if the plugin support the specified feature.
+ * @return {boolean} True if the plugin supports the specified feature.
  */
 remoting.ClientPlugin.prototype.hasFeature = function(feature) {};
 
@@ -215,20 +192,6 @@ remoting.ClientPlugin.prototype.setRouteChangedHandler = function(handler) {};
 remoting.ClientPlugin.prototype.setConnectionReadyHandler =
     function(handler) {};
 
-/**
- * @param {function():void} handler Callback for desktop size change
- *     notifications.
- */
-remoting.ClientPlugin.prototype.setDesktopSizeUpdateHandler =
-    function(handler) {};
-
-/**
- * @param {function(Array<Array<number>>):void} handler Callback for desktop
- *     shape change notifications.
- */
-remoting.ClientPlugin.prototype.setDesktopShapeUpdateHandler =
-    function(handler) {};
-
 /**
  * @param {function(!Array<string>):void} handler Callback to inform of
  *     capabilities negotiated between host and client.

remoting/webapp/crd/js/client_plugin_host_desktop_impl.js

+// Copyright 2015 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.
+
+/**
+ * @fileoverview
+ * Provides an interface to manage the Host Desktop of a remoting session.
+ */
+
+var remoting = remoting || {};
+remoting.ClientPlugin = remoting.ClientPlugin || {};
+
+(function() {
+
+'use strict';
+
+/**
+ * @param {remoting.ClientPluginImpl} plugin
+ * @param {function(Object):void} postMessageCallback Callback to post a message
+ *   to the Client Plugin.
+ *
+ * @implements {remoting.HostDesktop}
+ * @extends {base.EventSourceImpl}
+ * @constructor
+ */
+remoting.ClientPlugin.HostDesktopImpl = function(plugin, postMessageCallback) {
+  /** @private */
+  this.plugin_ = plugin;
+  /** @private */
+  this.width_ = 0;
+  /** @private */
+  this.height_ = 0;
+  /** @private */
+  this.xDpi_ = 96;
+  /** @private */
+  this.yDpi_ = 96;
+  /** @private */
+  this.postMessageCallback_ = postMessageCallback;
+
+  this.defineEvents(base.values(remoting.HostDesktop.Events));
+};
+base.extend(remoting.ClientPlugin.HostDesktopImpl, base.EventSourceImpl);
+
+/** @return {boolean} Whether the host supports desktop resizing. */
+remoting.ClientPlugin.HostDesktopImpl.prototype.isResizable = function() {
+  return this.plugin_.hasFeature(
+      remoting.ClientPlugin.Feature.NOTIFY_CLIENT_RESOLUTION);
+};
+
+/** @return {{width:number, height:number, xDpi:number, yDpi:number}} */
+remoting.ClientPlugin.HostDesktopImpl.prototype.getDimensions = function() {
+  return {
+    width: this.width_,
+    height: this.height_,
+    xDpi: this.xDpi_,
+    yDpi: this.yDpi_
+  };
+};
+
+/**
+ * @param {number} width
+ * @param {number} height
+ * @param {number} deviceScale
+ */
+remoting.ClientPlugin.HostDesktopImpl.prototype.resize = function(
+    width, height, deviceScale) {
+  if (this.isResizable()) {
+    var dpi = Math.floor(deviceScale * 96);
+    this.postMessageCallback_({
+      method: 'notifyClientResolution',
+      data: {
+        width: Math.floor(width * deviceScale),
+        height: Math.floor(height * deviceScale),
+        x_dpi: dpi,
+        y_dpi: dpi
+      }
+    });
+  }
+};
+
+/**
+ * This function is called by |this.plugin_| when the size of the host
+ * desktop is changed.
+ *
+ * @param {remoting.ClientPluginMessage} message
+ */
+remoting.ClientPlugin.HostDesktopImpl.prototype.onSizeUpdated = function(
+    message) {
+  this.width_ = getNumberAttr(message.data, 'width');
+  this.height_ = getNumberAttr(message.data, 'height');
+  this.xDpi_ = getNumberAttr(message.data, 'x_dpi', 96);
+  this.yDpi_ = getNumberAttr(message.data, 'y_dpi', 96);
+  this.raiseEvent(remoting.HostDesktop.Events.sizeChanged,
+                  this.getDimensions());
+};
+
+/**
+ * This function is called by |this.plugin_| when the shape of the host
+ * desktop is changed.
+ *
+ * @param {remoting.ClientPluginMessage} message
+ * @return {Array<{left:number, top:number, width:number, height:number}>}
+ *    rectangles of the desktop shape.
+ */
+remoting.ClientPlugin.HostDesktopImpl.prototype.onShapeUpdated =
+    function(message) {
+  var shapes = getArrayAttr(message.data, 'rects');
+  var rects = shapes.map(
+    /** @param {Array.<number>} shape */
+    function(shape) {
+      if (!Array.isArray(shape) || shape.length != 4) {
+        throw 'Received invalid onDesktopShape message';
+      }
+      var rect = {};
+      rect.left = shape[0];
+      rect.top = shape[1];
+      rect.width = shape[2];
+      rect.height = shape[3];
+      return rect;
+  });
+
+  this.raiseEvent(remoting.HostDesktop.Events.shapeChanged, rects);
+  return rects;
+};
+
+}());

remoting/webapp/crd/js/client_plugin_impl.js

@@ -48,15 +48,6 @@ remoting.ClientPluginImpl = function(container, onExtensionMessage,
    */
   this.requiredCapabilities_ = requiredCapabilities;
 
-  /** @private */
-  this.desktopWidth_ = 0;
-  /** @private */
-  this.desktopHeight_ = 0;
-  /** @private */
-  this.desktopXDpi_ = 96;
-  /** @private */
-  this.desktopYDpi_ = 96;
-
   /**
    * @param {string} iq The Iq stanza received from the host.
    * @private
@@ -95,13 +86,6 @@ remoting.ClientPluginImpl = function(container, onExtensionMessage,
    */
   this.fetchThirdPartyTokenHandler_ = function(
     tokenUrl, hostPublicKey, scope) {};
-  /** @private */
-  this.onDesktopSizeUpdateHandler_ = function () {};
-  /**
-   * @param {Array<Array<number>>} rects
-   * @private
-   */
-  this.onDesktopShapeUpdateHandler_ = function (rects) {};
   /**
    * @param {!Array<string>} capabilities The negotiated capabilities.
    * @private
@@ -180,6 +164,9 @@ remoting.ClientPluginImpl = function(container, onExtensionMessage,
   if (remoting.settings.CLIENT_PLUGIN_TYPE == 'native') {
     window.setTimeout(this.showPluginForClickToPlay_.bind(this), 500);
   }
+
+  this.hostDesktop_ = new remoting.ClientPlugin.HostDesktopImpl(
+      this, this.postMessage_.bind(this));
 };
 
 /**
@@ -264,22 +251,6 @@ remoting.ClientPluginImpl.prototype.setConnectionReadyHandler =
   this.onConnectionReadyHandler_ = handler;
 };
 
-/**
- * @param {function():void} handler
- */
-remoting.ClientPluginImpl.prototype.setDesktopSizeUpdateHandler =
-    function(handler) {
-  this.onDesktopSizeUpdateHandler_ = handler;
-};
-
-/**
- * @param {function(Array<Array<number>>):void} handler
- */
-remoting.ClientPluginImpl.prototype.setDesktopShapeUpdateHandler =
-    function(handler) {
-  this.onDesktopShapeUpdateHandler_ = handler;
-};
-
 /**
  * @param {function(!Array<string>):void} handler
  */
@@ -374,14 +345,6 @@ remoting.ClientPluginImpl.prototype.handleMessageMethod_ = function(message) {
           tokenize(getStringAttr(message.data, 'apiFeatures'));
 
       // Negotiate capabilities.
-
-      /** @type {!Array<string>} */
-      var requestedCapabilities = [];
-      if ('requestedCapabilities' in message.data) {
-        requestedCapabilities =
-            tokenize(getStringAttr(message.data, 'requestedCapabilities'));
-      }
-
       /** @type {!Array<string>} */
       var supportedCapabilities = [];
       if ('supportedCapabilities' in message.data) {
@@ -425,23 +388,9 @@ remoting.ClientPluginImpl.prototype.handleMessageMethod_ = function(message) {
     this.onRouteChangedHandler_(channel, connectionType);
 
   } else if (message.method == 'onDesktopSize') {
-    this.desktopWidth_ = getNumberAttr(message.data, 'width');
-    this.desktopHeight_ = getNumberAttr(message.data, 'height');
-    this.desktopXDpi_ = getNumberAttr(message.data, 'x_dpi', 96);
-    this.desktopYDpi_ = getNumberAttr(message.data, 'y_dpi', 96);
-    this.onDesktopSizeUpdateHandler_();
-
+    this.hostDesktop_.onSizeUpdated(message);
   } else if (message.method == 'onDesktopShape') {
-    var rects = getArrayAttr(message.data, 'rects');
-    for (var i = 0; i < rects.length; ++i) {
-      /** @type {Array<number>} */
-      var rect = rects[i];
-      if (typeof rect != 'object' || rect.length != 4) {
-        throw 'Received invalid onDesktopShape message';
-      }
-    }
-    this.onDesktopShapeUpdateHandler_(rects);
-
+    this.hostDesktop_.onShapeUpdated(message);
   } else if (message.method == 'onPerfStats') {
     // Return value is ignored. These calls will throw an error if the value
     // is not a number.
@@ -758,14 +707,7 @@ remoting.ClientPluginImpl.prototype.sendClipboardItem =
  */
 remoting.ClientPluginImpl.prototype.notifyClientResolution =
     function(width, height, device_scale) {
-  if (this.hasFeature(remoting.ClientPlugin.Feature.NOTIFY_CLIENT_RESOLUTION)) {
-    var dpi = Math.floor(device_scale * 96);
-    this.plugin_.postMessage(JSON.stringify(
-        { method: 'notifyClientResolution',
-          data: { width: Math.floor(width * device_scale),
-                  height: Math.floor(height * device_scale),
-                  x_dpi: dpi, y_dpi: dpi }}));
-  }
+  this.hostDesktop_.resize(width, height, device_scale);
 };
 
 /**
@@ -907,21 +849,9 @@ remoting.ClientPluginImpl.prototype.sendClientMessage =
 
 };
 
-remoting.ClientPluginImpl.prototype.getDesktopWidth = function() {
-  return this.desktopWidth_;
-}
-
-remoting.ClientPluginImpl.prototype.getDesktopHeight = function() {
-  return this.desktopHeight_;
-}
-
-remoting.ClientPluginImpl.prototype.getDesktopXDpi = function() {
-  return this.desktopXDpi_;
-}
-
-remoting.ClientPluginImpl.prototype.getDesktopYDpi = function() {
-  return this.desktopYDpi_;
-}
+remoting.ClientPluginImpl.prototype.hostDesktop = function() {
+  return this.hostDesktop_;
+};
 
 /**
  * If we haven't yet received a "hello" message from the plugin, change its
@@ -956,6 +886,17 @@ remoting.ClientPluginImpl.prototype.hidePluginForClickToPlay_ = function() {
   this.plugin_.style.position = '';
 };
 
+/**
+ * Callback passed to submodules to post a message to the plugin.
+ *
+ * @param {Object} message
+ * @private
+ */
+remoting.ClientPluginImpl.prototype.postMessage_ = function(message) {
+  if (this.plugin_ && this.plugin_.postMessage) {
+    this.plugin_.postMessage(JSON.stringify(message));
+  }
+};
 
 /**
  * @constructor

remoting/webapp/crd/js/client_session.js

@@ -244,6 +244,8 @@ remoting.ClientSession.Capability = {
 
   // Let the host know that we're interested in knowing whether or not it
   // rate limits desktop-resize requests.
+  // TODO(kelvinp): This has been supported since M-29.  Currently we only have
+  // <1000 users on M-29 or below. Remove this and the capability on the host.
   RATE_LIMIT_RESIZE_REQUESTS: 'rateLimitResizeRequests',
 
   // Indicates that host/client supports Google Drive integration, and that the

remoting/webapp/crd/js/desktop_connected_view.js

@@ -114,6 +114,11 @@ remoting.DesktopConnectedView = function(session, container, hostDisplayName,
 
   /** @type {remoting.VideoFrameRecorder} @private */
   this.videoFrameRecorder_ = null;
+
+  /** @private {base.Disposables} */
+  this.eventHooks_ = null;
+
+  this.defineEvents(base.values(remoting.DesktopConnectedView.Events));
 };
 
 base.extend(remoting.DesktopConnectedView, base.EventSourceImpl);
@@ -204,9 +209,9 @@ remoting.DesktopConnectedView.prototype.setPluginSizeForBumpScrollTesting =
  */
 remoting.DesktopConnectedView.prototype.notifyClientResolution_ = function() {
   var clientArea = this.getClientArea_();
-  this.plugin_.notifyClientResolution(clientArea.width * this.desktopScale_,
-                                      clientArea.height * this.desktopScale_,
-                                      window.devicePixelRatio);
+  this.plugin_.hostDesktop().resize(clientArea.width * this.desktopScale_,
+                                    clientArea.height * this.desktopScale_,
+                                    window.devicePixelRatio);
 };
 
 /**
@@ -303,10 +308,16 @@ remoting.DesktopConnectedView.prototype.onPluginInitialized_ = function(
     this.plugin_.allowMouseLock();
   }
 
-  this.plugin_.setDesktopShapeUpdateHandler(
-      this.onDesktopShapeChanged_.bind(this));
-  this.plugin_.setDesktopSizeUpdateHandler(
-      this.onDesktopSizeChanged_.bind(this));
+  base.dispose(this.eventHooks_);
+  var hostDesktop = this.plugin_.hostDesktop();
+  this.eventHooks_ = new base.Disposables(
+      new base.EventHook(
+        hostDesktop, remoting.HostDesktop.Events.sizeChanged,
+        this.onDesktopSizeChanged_.bind(this)),
+      new base.EventHook(
+        hostDesktop, remoting.HostDesktop.Events.shapeChanged,
+        this.onDesktopShapeChanged_.bind(this)));
+
   this.plugin_.setMouseCursorHandler(this.updateMouseCursorImage_.bind(this));
 
   this.onInitialized_(remoting.Error.NONE, this.plugin_);
@@ -320,11 +331,12 @@ remoting.DesktopConnectedView.prototype.onPluginInitialized_ = function(
  * @private
  */
 remoting.DesktopConnectedView.prototype.onDesktopSizeChanged_ = function() {
+  var desktop = this.plugin_.hostDesktop().getDimensions();
   console.log('desktop size changed: ' +
-              this.plugin_.getDesktopWidth() + 'x' +
-              this.plugin_.getDesktopHeight() +' @ ' +
-              this.plugin_.getDesktopXDpi() + 'x' +
-              this.plugin_.getDesktopYDpi() + ' DPI');
+              desktop.width + 'x' +
+              desktop.height +' @ ' +
+              desktop.xDpi + 'x' +
+              desktop.yDpi + ' DPI');
   this.updateDimensions();
   this.updateScrollbarVisibility();
 };
@@ -370,11 +382,7 @@ remoting.DesktopConnectedView.prototype.onResize = function() {
   // Defer notifying the host of the change until the window stops resizing, to
   // avoid overloading the control channel with notifications.
   if (this.resizeToClient_) {
-    var kResizeRateLimitMs = 1000;
-    if (this.session_.hasCapability(
-        remoting.ClientSession.Capability.RATE_LIMIT_RESIZE_REQUESTS)) {
-      kResizeRateLimitMs = 250;
-    }
+    var kResizeRateLimitMs = 250;
     var clientArea = this.getClientArea_();
     this.notifyClientResolutionTimer_ = window.setTimeout(
         this.notifyClientResolution_.bind(this),
@@ -411,6 +419,8 @@ remoting.DesktopConnectedView.prototype.onConnectionReady = function(ready) {
  */
 remoting.DesktopConnectedView.prototype.removePlugin = function() {
   if (this.plugin_) {
+    base.dispose(this.eventHooks_);
+    this.eventHooks_ = null;
     this.plugin_.element().removeEventListener(
         'focus', this.callPluginGotFocus_, false);
     this.plugin_.element().removeEventListener(
@@ -744,15 +754,15 @@ remoting.DesktopConnectedView.prototype.scroll_ = function(dx, dy) {
  * @return {void} Nothing.
  */
 remoting.DesktopConnectedView.prototype.updateDimensions = function() {
-  if (this.plugin_.getDesktopWidth() == 0 ||
-      this.plugin_.getDesktopHeight() == 0) {
+  var desktopSize = this.plugin_.hostDesktop().getDimensions();
+
+  if (desktopSize.width === 0 ||
+      desktopSize.height === 0) {
     return;
   }
 
-  var desktopSize = { width: this.plugin_.getDesktopWidth(),
-                      height: this.plugin_.getDesktopHeight() };
-  var desktopDpi = { x: this.plugin_.getDesktopXDpi(),
-                     y: this.plugin_.getDesktopYDpi() };
+  var desktopDpi = { x: desktopSize.xDpi,
+                     y: desktopSize.yDpi };
   var newSize = remoting.DesktopConnectedView.choosePluginSize(
       this.getClientArea_(), window.devicePixelRatio,
       desktopSize, desktopDpi, this.desktopScale_,
@@ -920,15 +930,16 @@ remoting.DesktopConnectedView.prototype.updateScrollbarVisibility = function() {
     // Determine whether or not horizontal or vertical scrollbars are
     // required, taking into account their width.
     var clientArea = this.getClientArea_();
-    needsVerticalScroll = clientArea.height < this.plugin_.getDesktopHeight();
-    needsHorizontalScroll = clientArea.width < this.plugin_.getDesktopWidth();
+    var desktopSize = this.plugin_.hostDesktop().getDimensions();
+    needsVerticalScroll = clientArea.height < desktopSize.height;
+    needsHorizontalScroll = clientArea.width < desktopSize.width;
     var kScrollBarWidth = 16;
     if (needsHorizontalScroll && !needsVerticalScroll) {
       needsVerticalScroll =
-          clientArea.height - kScrollBarWidth < this.plugin_.getDesktopHeight();
+          clientArea.height - kScrollBarWidth < desktopSize.height;
     } else if (!needsHorizontalScroll && needsVerticalScroll) {
       needsHorizontalScroll =
-          clientArea.width - kScrollBarWidth < this.plugin_.getDesktopWidth();
+          clientArea.width - kScrollBarWidth < desktopSize.width;
     }
   }
 

remoting/webapp/crd/js/host_desktop.js

+// Copyright 2015 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.
+
+/**
+ * @fileoverview
+ * Interface abstracting the functionality of the HostDesktop.
+ */
+
+var remoting = remoting || {};
+
+(function() {
+
+'use strict';
+
+/**
+ * @interface
+ * @extends {base.EventSource}
+ */
+remoting.HostDesktop = function() {};
+
+/** @return {boolean} Whether the host supports desktop resizing. */
+remoting.HostDesktop.prototype.isResizable = function() {};
+
+/** @enum {string} */
+remoting.HostDesktop.Events = {
+  // Fired when the size of the host desktop changes with the desktop dimensions
+  //  {{width:number, height:number, xDpi:number, yDpi:number}}
+  sizeChanged: 'sizeChanged',
+  // Fired when the shape of the host desktop changes with an array of
+  // rectangles of desktop shapes as the event data.
+  //   Array<{left:number, top:number, width:number, height:number}>
+  shapeChanged: 'shapeChanged'
+};
+
+/**
+ * @return {{width:number, height:number, xDpi:number, yDpi:number}}
+ *  The dimensions and DPI settings of the host desktop.
+ */
+remoting.HostDesktop.prototype.getDimensions = function() {};
+
+/**
+ * Resize the desktop of the host to |width|, |height| and |deviceScale|.
+ *
+ * @param {number} width The width of the desktop in DIPs.
+ * @param {number} height The height of the desktop in DIPs.
+ * @param {number} deviceScale
+ */
+remoting.HostDesktop.prototype.resize = function(width, height, deviceScale) {};
+
+})();