Not submitted - Fixing invalid visibility states with layers which showed up in unittests ...

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 9392303b8518bb5a68eb7cfd85da073e0c6fd955..6ac06745bf842f40eb1e0f6f2de4a1e6cfc56d44 100644
--- a/ash/wm/panels/panel_layout_manager.cc
+++ b/ash/wm/panels/panel_layout_manager.cc
@@ -57,6 +57,11 @@ const int kPanelSlideInOffset = 20;
 const int kArrowWidth = 18;
 const int kArrowHeight = 9;
 
+// When a window layer gets hidden, and the window remains "logically visible",
+// it is illegal to fade the layer to 0. We therefore use a fraction which is
+// resolving to an alpha of 0 but tells a comparison otherwise.
+const float kWindowLayerNotShown = 0.001f;
+
 class CalloutWidgetBackground : public views::Background {
  public:
   CalloutWidgetBackground() : alignment_(SHELF_ALIGNMENT_BOTTOM) {
@@ -243,7 +248,7 @@ class PanelCalloutWidget : public views::Widget {
     background_ = new CalloutWidgetBackground;
     content_view->set_background(background_);
     SetContentsView(content_view);
-    GetNativeWindow()->layer()->SetOpacity(0);
+    GetNativeWindow()->layer()->SetOpacity(kWindowLayerNotShown);
   }
 
   // Weak pointer owned by this widget's content view.
@@ -366,7 +371,7 @@ void PanelLayoutManager::OnWindowAddedToLayout(aura::Window* child) {
   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);
+    child->layer()->SetOpacity(kWindowLayerNotShown);
     panel_info.slide_in = true;
   }
   panel_windows_.push_back(panel_info);
@@ -561,7 +566,7 @@ void PanelLayoutManager::MinimizePanel(aura::Window* panel) {
   PanelList::iterator found =
       std::find(panel_windows_.begin(), panel_windows_.end(), panel);
   if (found != panel_windows_.end()) {
-    layer->SetOpacity(0);
+    layer->SetOpacity(kWindowLayerNotShown);
     // The next time the window is visible it should slide into place.
     found->slide_in = true;
   }
@@ -857,12 +862,12 @@ void PanelLayoutManager::UpdateCallouts() {
         panel->layer()->GetTargetTransform().IsIdentity()) {
       if (distance_until_over_panel > 0 &&
           slide_distance >= distance_until_over_panel) {
-        layer->SetOpacity(0);
+        layer->SetOpacity(kWindowLayerNotShown);
         // If the panel is not yet over the callout, then delay fading in
         // the callout until after the panel should be over it.
         int delay = kPanelSlideDurationMilliseconds *
             distance_until_over_panel / slide_distance;
-        layer->SetOpacity(0);
+        layer->SetOpacity(kWindowLayerNotShown);
         layer->GetAnimator()->StopAnimating();
         layer->GetAnimator()->SchedulePauseForProperties(
             base::TimeDelta::FromMilliseconds(delay),