[CRD iOS] Some fixes for rendering

remoting/ios/session/remoting_client.mm

 // Copyright 2017 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.
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
 #endif
 
 #import "remoting/ios/session/remoting_client.h"
 
@@ skipping 115 matching lines @@
       base::BindBlockArc(^(const remoting::ViewMatrix& matrix) {
         [weakDisplayHandler onPixelTransformationChanged:matrix];
       }),
       _session.get()));
 }
 
 - (void)disconnectFromHost {
   if (_session) {
     _session->Disconnect();
   }
+  _displayHandler = nil;
   // TODO(nicholss): Do we need to cleanup more?
 }
 
 #pragma mark - Eventing
 
 - (void)hostSessionPinProvided:(NSNotification*)notification {
   NSString* pin = [[notification userInfo] objectForKey:kHostSessionPin];
   if (_secretFetchedCallback) {
     _runtime->network_task_runner()->PostTask(
         FROM_HERE, base::BindBlockArc(^{
@@ skipping 69 matching lines @@
   NSLog(@"TODO(nicholss): implement this, setCapabilities.");
 }
 
 - (void)handleExtensionMessageOfType:(NSString*)type
                              message:(NSString*)message {
   NSLog(@"TODO(nicholss): implement this, handleExtensionMessageOfType %@:%@.",
         type, message);
 }
 
 - (void)surfaceChanged:(const CGRect&)frame {
+  // Note that GLKView automatically sets the OpenGL viewport size to the size
+  // of the surface.
   [_displayHandler onSurfaceChanged:frame];
   _gestureInterpreter->OnSurfaceSizeChanged(frame.size.width,
                                             frame.size.height);
 }
 
 #pragma mark - GlDisplayHandlerDelegate
 
 - (void)canvasSizeChanged:(CGSize)size {
   if (_gestureInterpreter) {
     _gestureInterpreter->OnDesktopSizeChanged(size.width, size.height);
   }
 }
 
 @end