Replace WmWindowObserver with aura::WindowObserver.

ash/common/wm/window_dimmer.cc

Index: ash/common/wm/window_dimmer.cc
diff --git a/ash/common/wm/window_dimmer.cc b/ash/common/wm/window_dimmer.cc
index bdd1109d9905c3b44ed9da1b3902386006559ade..c90d806832fe21d6b24aa82e6689315fee2209f6 100644
--- a/ash/common/wm/window_dimmer.cc
+++ b/ash/common/wm/window_dimmer.cc
@@ -9,6 +9,7 @@
 #include "ash/common/wm_shell.h"
 #include "ash/common/wm_window.h"
 #include "base/time/time.h"
+#include "ui/aura/window.h"
 #include "ui/compositor/layer.h"
 #include "ui/wm/core/window_animations.h"
 
@@ -30,12 +31,12 @@ WindowDimmer::WindowDimmer(WmWindow* parent)
       ::wm::WINDOW_VISIBILITY_ANIMATION_TYPE_FADE);
   window_->SetVisibilityAnimationDuration(
       base::TimeDelta::FromMilliseconds(kDefaultDimAnimationDurationMs));
-  window_->AddObserver(this);
+  window_->aura_window()->AddObserver(this);
 
   SetDimOpacity(kDefaultDimOpacity);
 
   parent->AddChild(window_);
-  parent->AddObserver(this);
+  parent->aura_window()->AddObserver(this);
   parent->StackChildAtTop(window_);
 
   window_->SetBounds(gfx::Rect(parent_->GetBounds().size()));
@@ -43,9 +44,9 @@ WindowDimmer::WindowDimmer(WmWindow* parent)
 
 WindowDimmer::~WindowDimmer() {
   if (parent_)
-    parent_->RemoveObserver(this);
+    parent_->aura_window()->RemoveObserver(this);
   if (window_) {
-    window_->RemoveObserver(this);
+    window_->aura_window()->RemoveObserver(this);
     window_->Destroy();
   }
 }
@@ -56,27 +57,28 @@ void WindowDimmer::SetDimOpacity(float target_opacity) {
       SkColorSetA(SK_ColorBLACK, 255 * target_opacity));
 }
 
-void WindowDimmer::OnWindowBoundsChanged(WmWindow* window,
+void WindowDimmer::OnWindowBoundsChanged(aura::Window* window,
                                          const gfx::Rect& old_bounds,
                                          const gfx::Rect& new_bounds) {
-  if (window == parent_)
+  if (WmWindow::Get(window) == parent_)
     window_->SetBounds(gfx::Rect(new_bounds.size()));
 }
 
-void WindowDimmer::OnWindowDestroying(WmWindow* window) {
-  if (window == parent_) {
-    parent_->RemoveObserver(this);
+void WindowDimmer::OnWindowDestroying(aura::Window* window) {
+  if (WmWindow::Get(window) == parent_) {
+    parent_->aura_window()->RemoveObserver(this);
     parent_ = nullptr;
   } else {
-    DCHECK_EQ(window_, window);
-    window_->RemoveObserver(this);
+    DCHECK_EQ(window_, WmWindow::Get(window));
+    window_->aura_window()->RemoveObserver(this);
     window_ = nullptr;
   }
 }
 
-void WindowDimmer::OnWindowTreeChanging(WmWindow* window,
-                                        const TreeChangeParams& params) {
-  if (window == window_ && params.target == window) {
+void WindowDimmer::OnWindowHierarchyChanging(
+    const HierarchyChangeParams& params) {
+  if (WmWindow::Get(params.receiver) == window_ &&
+      params.target == params.receiver) {
     // This may happen on a display change or some unexpected condition. Hide
     // the window to ensure it isn't obscuring the wrong thing.
     window_->Hide();