Ensure View invalidates Widget::root_layers_ when LayerOwner::RecreateLayer is invoked

ash/wm/window_state_unittest.cc

Index: ash/wm/window_state_unittest.cc
diff --git a/ash/wm/window_state_unittest.cc b/ash/wm/window_state_unittest.cc
index d816cf7d11ba78e0f66a6fd659b7367f98e785fa..cbb6ab5855a18491e24607adc79beaa64b1ec1cb 100644
--- a/ash/wm/window_state_unittest.cc
+++ b/ash/wm/window_state_unittest.cc
@@ -12,6 +12,7 @@
 #include "ui/aura/client/aura_constants.h"
 #include "ui/aura/test/test_window_delegate.h"
 #include "ui/aura/window.h"
+#include "ui/views/widget/widget.h"
 
 namespace ash {
 namespace wm {
@@ -337,5 +338,32 @@ TEST_F(WindowStateTest, RestoredWindowBoundsShrink) {
 // TODO(skuhne): Add more unit test to verify the correctness for the restore
 // operation.
 
+// Tests for correct ownership of window sublayers during crossfade transitions.
+TEST_F(WindowStateTest, RecreateLayersDuringCrossfade) {

[sky, 2015/11/30 16:52:09]

This test is ok, but you're relying on maximize recreating layers. How about
directly calling RecreateLayers?

[tapted, 2015/12/01 04:34:43]

I did this in Patchset 4, but it made the connection to ash/../window_state a
bit tenuous. Also it started looking a lot like the existing test in
view_unittest_aura for wm::RecreateLayers

So I've incorporated the test cases into view_unittest_aura's
ViewAuraTest.RecreateLayersWithWindows - I think this make sense. It also has
the advantage of being run on more platforms, instead of just those running
ash_unittests. PTAL

+  views::Widget* widget = views::Widget::CreateWindowWithContextAndBounds(
+      nullptr, CurrentContext(), gfx::Rect(100, 100, 100, 100));
+
+  views::View* view = new views::View;
+  view->SetBounds(20, 20, 20, 20);
+  widget->GetContentsView()->AddChildView(view);
+  widget->Show();
+
+  EXPECT_EQ(0u, widget->GetRootLayers().size());
+  view->SetPaintToLayer(true);
+  EXPECT_EQ(1u, widget->GetRootLayers().size());
+  ui::Layer* old_layer = widget->GetRootLayers()[0];
+
+  // On Ash, Maximize will trigger WindowState::SetBoundsDirectCrossFade() to
+  // start a crossfade animation after invoking ::wm::RecreateLayers().
+  widget->Maximize();
+
+  EXPECT_EQ(1u, widget->GetRootLayers().size());
+
+  // The layer should be different, since the old layer is in the crossfade.
+  EXPECT_NE(old_layer, widget->GetRootLayers()[0]);
+
+  widget->CloseNow();
+}
+
 }  // namespace wm
 }  // namespace ash