[CRD iOS] Some fixes for rendering

remoting/ios/app/host_view_controller.mm

Index: remoting/ios/app/host_view_controller.mm
diff --git a/remoting/ios/app/host_view_controller.mm b/remoting/ios/app/host_view_controller.mm
index 30b19c417349ef07c04fe3de32afb30e462b3490..e866d7691469a9b691043ca4f52103db509ec5d7 100644
--- a/remoting/ios/app/host_view_controller.mm
+++ b/remoting/ios/app/host_view_controller.mm
@@ -75,11 +75,16 @@ static const CGFloat kFabInset = 15.f;
   [_client.displayHandler onSurfaceCreated:glView];
 
   // viewDidLayoutSubviews may be called before viewDidAppear, in which case
-  // the surface is not ready and onSurfaceChanged will be no-op.
+  // the surface is not ready to handle the transformation matrix.
   // Call onSurfaceChanged here to cover that case.
   [_client surfaceChanged:self.view.frame];
 }
 
+- (void)viewDidDisappear:(BOOL)animated {
+  [super viewDidDisappear:animated];
+  [(GLKView*)self.view deleteDrawable];
+}
+
 - (void)viewWillAppear:(BOOL)animated {
   [super viewWillAppear:animated];
 
@@ -96,7 +101,11 @@ static const CGFloat kFabInset = 15.f;
 - (void)viewDidLayoutSubviews {
   [super viewDidLayoutSubviews];
 
-  [_client surfaceChanged:self.view.frame];
+  if (((GLKView*)self.view).context != nil) {
+    // If the context is not set yet, the view size will be set in
+    // viewDidAppear.
+    [_client surfaceChanged:self.view.bounds];
+  }
 
   CGSize btnSize = _floatingButton.frame.size;
   _floatingButton.frame =