Unify window fullscreen and minimizing implementation

ash/common/wm_window.cc

Index: ash/common/wm_window.cc
diff --git a/ash/common/wm_window.cc b/ash/common/wm_window.cc
index 74c64d6e5a579ac1eb7a2b4aeb4e12862150a424..21281fd6197dc4782a958ff33dd4013450d69869 100644
--- a/ash/common/wm_window.cc
+++ b/ash/common/wm_window.cc
@@ -610,6 +610,7 @@ ui::WindowShowState WmWindow::GetShowState() const {
 }
 
 void WmWindow::SetPreMinimizedShowState(ui::WindowShowState show_state) {
+  DCHECK_NE(show_state, ui::SHOW_STATE_PREVIOUS);
   window_->SetProperty(aura::client::kPreMinimizedShowStateKey, show_state);
 }
 
@@ -621,6 +622,7 @@ void WmWindow::SetPreFullscreenShowState(ui::WindowShowState show_state) {
   // We should never store the ui::SHOW_STATE_MINIMIZED as the show state before
   // fullscreen.
   DCHECK_NE(show_state, ui::SHOW_STATE_MINIMIZED);
+  DCHECK_NE(show_state, ui::SHOW_STATE_PREVIOUS);
   window_->SetProperty(aura::client::kPreFullscreenShowStateKey, show_state);
 }
 
@@ -772,6 +774,7 @@ void WmWindow::SetFullscreen(bool fullscreen) {
   } else {
     auto state = window_->GetProperty(aura::client::kPreFullscreenShowStateKey);
     DCHECK_NE(state, ui::SHOW_STATE_MINIMIZED);
+    DCHECK_NE(state, ui::SHOW_STATE_PREVIOUS);
     window_->SetProperty(aura::client::kShowStateKey, state);
     window_->ClearProperty(aura::client::kPreFullscreenShowStateKey);
   }
@@ -942,7 +945,19 @@ void WmWindow::OnWindowPropertyChanged(aura::Window* window,
                                        const void* key,
                                        intptr_t old) {
   if (key == aura::client::kShowStateKey) {
-    ash::wm::GetWindowState(window_)->OnWindowShowStateChanged();
+    ui::WindowShowState state = GetShowState();
+    if (state == ui::SHOW_STATE_PREVIOUS) {
+      ui::WindowShowState old_state = static_cast<ui::WindowShowState>(old);
+      if (old_state == ui::SHOW_STATE_FULLSCREEN) {
+        SetFullscreen(false);
+      } else if (old_state == ui::SHOW_STATE_MINIMIZED) {
+        Unminimize();
+      } else {
+        NOTREACHED();
+      }
+    } else {
+      ash::wm::GetWindowState(window_)->OnWindowShowStateChanged();
+    }
     return;
   }
   WmWindowProperty wm_property;