When we switch tabs in chrome, the tab being switched away from gets hidden/shown/hidden.

ui/views/widget/native_widget_aura.cc

Index: ui/views/widget/native_widget_aura.cc
diff --git a/ui/views/widget/native_widget_aura.cc b/ui/views/widget/native_widget_aura.cc
index b436c8eeeb13e64bcf76829b8827521254693b5f..a7a71687e0d6847e9b2358a003a2d36f197fa18b 100644
--- a/ui/views/widget/native_widget_aura.cc
+++ b/ui/views/widget/native_widget_aura.cc
@@ -1148,8 +1148,10 @@ void NativeWidgetPrivate::ReparentNativeView(gfx::NativeView native_view,
     // matches our previous behaviour; the global stacking client would almost
     // always reattach the window to the same RootWindow.
     aura::Window* root_window = native_view->GetRootWindow();
-    aura::client::ParentWindowWithContext(
-        native_view, root_window, root_window->GetBoundsInScreen());
+    if (root_window) {

[sky, 2014/09/12 21:27:05]

This makes me nervous. See big comment above this. Under what conditions are we
now getting here with no parent? Who was the window previously parented to?

[ananta, 2014/09/14 01:30:44]

As per discussion, added code to show hide the WebContents view in
AttachWebContents/DetachWebContents. The webcontents instance is show/hidden by
the window visible observer in WebContentsViewAura as before. 

Added a new file webview unittest.cc which run as part of unit_tests.exe. This
file contains one test which verifies attach/detach webcontents and visibility.

+      aura::client::ParentWindowWithContext(
+          native_view, root_window, root_window->GetBoundsInScreen());
+    }
   }
 
   // And now, notify them that they have a brand new parent.