Couple of fixes for DesktopWindowTreeHostMus.

ui/views/mus/desktop_window_tree_host_mus.cc

Index: ui/views/mus/desktop_window_tree_host_mus.cc
diff --git a/ui/views/mus/desktop_window_tree_host_mus.cc b/ui/views/mus/desktop_window_tree_host_mus.cc
index d5464b6a1561081aa1d368c5041d8e612e43043c..b8387f0dbc2dec32563811218732d933a6e8efc0 100644
--- a/ui/views/mus/desktop_window_tree_host_mus.cc
+++ b/ui/views/mus/desktop_window_tree_host_mus.cc
@@ -46,7 +46,11 @@ bool DesktopWindowTreeHostMus::IsDocked() const {
 }
 
 void DesktopWindowTreeHostMus::Init(aura::Window* content_window,
-                                    const Widget::InitParams& params) {}
+                                    const Widget::InitParams& params) {
+  // TODO: handle device scale, http://crbug.com/663524.
+  if (!params.bounds.IsEmpty())
+    SetBounds(params.bounds);
+}
 
 void DesktopWindowTreeHostMus::OnNativeWidgetCreated(
     const Widget::InitParams& params) {
@@ -110,8 +114,8 @@ void DesktopWindowTreeHostMus::ShowWindowWithState(ui::WindowShowState state) {
   window()->Show();
   if (compositor())
     compositor()->SetVisible(true);
-  // TODO: likely needs code to activate, but after content_window_ is shown.
-  // See NativeWidgetAura::ShowWithWindowState().
+
+  native_widget_delegate_->AsWidget()->SetInitialFocus(state);

[msw, 2016/11/10 18:27:45]

q: Should this check if native_widget_delgate_->CanActivate like
NativeWidgetMus? Also, do we care about the return value like NativeWidgetAura?
"Returns true if the initial focus has been set or the window should not set the
initial focus, or false if the caller should set the initial focus (if any)."

[sky, 2016/11/10 20:18:11]

I'm not exactly sure. That doesn't exist in the desktopwindowtreehost impls,
which seems weird. But I added it here for consistency.

 }
 
 void DesktopWindowTreeHostMus::ShowMaximizedWithBounds(
@@ -152,7 +156,33 @@ void DesktopWindowTreeHostMus::StackAtTop() {
 }
 
 void DesktopWindowTreeHostMus::CenterWindow(const gfx::Size& size) {
-  NOTIMPLEMENTED();
+  gfx::Rect bounds_to_center_in = GetWorkAreaBoundsInScreen();
+
+  // If there is a transient parent and it fits |size|, then center over it.
+  aura::Window* content_window = desktop_native_widget_aura_->content_window();
+  if (wm::GetTransientParent(content_window)) {
+    gfx::Rect transient_parent_bounds =
+        wm::GetTransientParent(content_window)->GetBoundsInScreen();
+    if (transient_parent_bounds.height() >= size.height() &&
+        transient_parent_bounds.width() >= size.width()) {
+      bounds_to_center_in = transient_parent_bounds;
+    }
+  }
+
+  gfx::Rect resulting_bounds(

[msw, 2016/11/10 18:27:45]

Use gfx::Rect::ClampToCenteredSize, then skip AdjustToFit?

[sky, 2016/11/10 20:18:11]

Good call! Done.

+      bounds_to_center_in.x() +
+          (bounds_to_center_in.width() - size.width()) / 2,
+      bounds_to_center_in.y() +
+          (bounds_to_center_in.height() - size.height()) / 2,
+      size.width(), size.height());
+
+  // Don't size the window bigger than the parent, otherwise the user may not be
+  // able to close or move it.
+  resulting_bounds.AdjustToFit(bounds_to_center_in);
+
+  // TODO: handle device scale, http://crbug.com/663524. SetBounds() expects
+  // pixels.
+  SetBounds(resulting_bounds);
 }
 
 void DesktopWindowTreeHostMus::GetWindowPlacement(
@@ -261,7 +291,10 @@ bool DesktopWindowTreeHostMus::IsMinimized() const {
 }
 
 bool DesktopWindowTreeHostMus::HasCapture() const {
-  return const_cast<aura::Window*>(window())->HasCapture();
+  // Capture state is held by DesktopNativeWidgetAura::content_window_.
+  // DesktopNativeWidgetAura::HasCapture() calls content_window_->HasCapture(),
+  // and this. That means this function can always return true.
+  return true;
 }
 
 void DesktopWindowTreeHostMus::SetAlwaysOnTop(bool always_on_top) {