Fix some thread safety violations in device::GvrDelegate implementation.

chrome/browser/android/vr_shell/vr_compositor.cc

 // Copyright 2016 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.
 
 #include "chrome/browser/android/vr_shell/vr_compositor.h"
 
 #include "cc/layers/layer.h"
 #include "content/public/browser/android/compositor.h"
 #include "content/public/browser/web_contents.h"
 #include "third_party/skia/include/core/SkColor.h"
@@ skipping 36 matching lines @@
     layer_->SetBackgroundColor(SK_ColorTRANSPARENT);
   }
   layer_parent_ = layer_->parent();
   compositor_->SetRootLayer(layer_);
 }
 
 void VrCompositor::SurfaceDestroyed() {
   compositor_->SetSurface(nullptr);
 }
 
-void VrCompositor::SetWindowBounds(int width, int height) {
-  compositor_->SetWindowBounds(gfx::Size(width, height));
+void VrCompositor::SetWindowBounds(gfx::Size size) {
+  bounds_ = size;
+  compositor_->SetWindowBounds(bounds_);
 }
 
 void VrCompositor::SurfaceChanged(jobject surface) {
   DCHECK(surface);
   compositor_->SetSurface(surface);
 }
 
 }  // namespace vr_shell