Revert of Remove remaining window states where window is shown with opacity 0.

ash/wm/panels/panel_layout_manager.cc

Index: ash/wm/panels/panel_layout_manager.cc
diff --git a/ash/wm/panels/panel_layout_manager.cc b/ash/wm/panels/panel_layout_manager.cc
index 8954e57f39e4dbb41c8799e48962fe1a5320cf57..9266f94bb1cff1be678a2133d81299322debe184 100644
--- a/ash/wm/panels/panel_layout_manager.cc
+++ b/ash/wm/panels/panel_layout_manager.cc
@@ -11,7 +11,6 @@
 #include "ash/shelf/shelf.h"
 #include "ash/shelf/shelf_layout_manager.h"
 #include "ash/shelf/shelf_types.h"
-#include "ash/shelf/shelf_util.h"
 #include "ash/shelf/shelf_widget.h"
 #include "ash/shell.h"
 #include "ash/shell_window_ids.h"
@@ -364,9 +363,13 @@
   PanelInfo panel_info;
   panel_info.window = child;
   panel_info.callout_widget = new PanelCalloutWidget(panel_container_);
-  panel_info.slide_in = child != dragged_panel_;
+  if (child != dragged_panel_) {
+    // Set the panel to 0 opacity until it has been positioned to prevent it
+    // from flashing briefly at position (0, 0).
+    child->layer()->SetOpacity(0);
+    panel_info.slide_in = true;
+  }
   panel_windows_.push_back(panel_info);
-  child->AddObserver(this);
   wm::GetWindowState(child)->AddObserver(this);
   Relayout();
 }
@@ -383,9 +386,6 @@
     delete found->callout_widget;
     panel_windows_.erase(found);
   }
-  if (restore_windows_on_shelf_visible_)
-    restore_windows_on_shelf_visible_->Remove(child);
-  child->RemoveObserver(this);
   wm::GetWindowState(child)->RemoveObserver(this);
 
   if (dragged_panel_ == child)
@@ -458,18 +458,6 @@
 
 /////////////////////////////////////////////////////////////////////////////
 // PanelLayoutManager, WindowObserver implementation:
-
-void PanelLayoutManager::OnWindowPropertyChanged(aura::Window* window,
-                                                 const void* key,
-                                                 intptr_t old) {
-  // Trigger a relayout to position the panels whenever the panel icon is set
-  // or changes.
-  if (key == kShelfID)
-    Relayout();
-}
-
-/////////////////////////////////////////////////////////////////////////////
-// PanelLayoutManager, WindowStateObserver implementation:
 
 void PanelLayoutManager::OnPostWindowStateTypeChange(
     wm::WindowState* window_state,
@@ -564,17 +552,20 @@
       shelf_->shelf_widget()->GetAlignment()));
   SetChildBoundsDirect(panel, bounds);
   panel->Hide();
-  layer->SetOpacity(0);
+  PanelList::iterator found =
+      std::find(panel_windows_.begin(), panel_windows_.end(), panel);
+  if (found != panel_windows_.end()) {
+    layer->SetOpacity(0);
+    // The next time the window is visible it should slide into place.
+    found->slide_in = true;
+  }
   if (wm::IsActiveWindow(panel))
     wm::DeactivateWindow(panel);
   Relayout();
 }
 
 void PanelLayoutManager::RestorePanel(aura::Window* panel) {
-  PanelList::iterator found =
-      std::find(panel_windows_.begin(), panel_windows_.end(), panel);
-  DCHECK(found != panel_windows_.end());
-  found->slide_in = true;
+  panel->Show();
   Relayout();
 }
 
@@ -604,7 +595,7 @@
 
     // Consider the dragged panel as part of the layout as long as it is
     // touching the shelf.
-    if ((!panel->IsVisible() && !iter->slide_in) ||
+    if (!panel->IsVisible() ||
         (panel == dragged_panel_ &&
          !BoundsAdjacent(panel->bounds(), shelf_bounds))) {
       continue;
@@ -707,8 +698,7 @@
 
     ui::Layer* layer = visible_panels[i].window->layer();
     if (slide_in) {
-      // New windows shift up from the shelf into position and fade in.
-      layer->SetOpacity(0);
+      // New windows shift up from the shelf into position.
       gfx::Rect initial_bounds(bounds);
       initial_bounds.Offset(GetSlideInAnimationOffset(alignment));
       SetChildBoundsDirect(visible_panels[i].window, initial_bounds);
@@ -724,10 +714,8 @@
       panel_slide_settings.SetTransitionDuration(
           base::TimeDelta::FromMilliseconds(kPanelSlideDurationMilliseconds));
       SetChildBoundsDirect(visible_panels[i].window, bounds);
-      if (slide_in) {
+      if (slide_in)
         layer->SetOpacity(1);
-        visible_panels[i].window->Show();
-      }
     } else {
       // If the shelf moved don't animate, move immediately to the new
       // target location.