Initialize stub platform window bounds to those of its mus::Window.

ui/views/mus/window_tree_host_mus.cc

 // 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.
 
 #include "ui/views/mus/window_tree_host_mus.h"
 
 #include "base/memory/ptr_util.h"
 #include "components/bitmap_uploader/bitmap_uploader.h"
 #include "components/mus/public/cpp/window.h"
 #include "ui/aura/window.h"
@@ skipping 36 matching lines @@
   if (connector) {
     bitmap_uploader_.reset(new bitmap_uploader::BitmapUploader(window));
     bitmap_uploader_->Init(connector);
     prop_.reset(
         new ui::ViewProp(accelerated_widget,
                          bitmap_uploader::kBitmapUploaderForAcceleratedWidget,
                          bitmap_uploader_.get()));
   }
 
   SetPlatformWindow(base::WrapUnique(new ui::StubWindow(nullptr)));
+  // Initialize the stub platform window bounds to those of the mus::Window.
+  platform_window()->SetBounds(window->bounds());

[sky, 2016/06/03 22:12:52]

This seems right to me. I see another bug, will file it separately.

 
   // The location of events is already transformed, and there is no way to
   // correctly determine the reverse transform. So, don't attempt to transform
   // event locations, else the root location is wrong.
   // TODO(sky): we need to transform for device scale though.
   dispatcher()->set_transform_events(false);
   compositor()->SetHostHasTransparentBackground(true);
 
   input_method_.reset(new InputMethodMUS(this, window));
   SetSharedInputMethod(input_method_.get());
@@ skipping 26 matching lines @@
   if (native_widget_)
     native_widget_->OnActivationChanged(active);
   WindowTreeHostPlatform::OnActivationChanged(active);
 }
 
 void WindowTreeHostMus::OnCloseRequest() {
   OnHostCloseRequested();
 }
 
 }  // namespace views