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

ui/views/widget/native_widget_aura.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/views/widget/native_widget_aura.h"
 
 #include "base/bind.h"
 #include "base/strings/string_util.h"
 #include "third_party/skia/include/core/SkRegion.h"
 #include "ui/aura/client/aura_constants.h"
@@ skipping 1130 matching lines @@
     // NULL as a special value that meant ask the WindowTreeClient where things
     // should go.)
     //
     // This probably isn't strictly correct, but its an invariant that a Window
     // in use will be attached to a RootWindow, so we can't just call
     // RemoveChild here. The only possible thing that could assign a RootWindow
     // in this case is the stacking client of the current RootWindow. This
     // 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.
   for (Widget::Widgets::iterator it = widgets.begin();
       it != widgets.end(); ++it) {
     (*it)->NotifyNativeViewHierarchyChanged();
   }
 }
 
 // static
 bool NativeWidgetPrivate::IsMouseButtonDown() {
   return aura::Env::GetInstance()->IsMouseButtonDown();
 }
 
 // static
 gfx::FontList NativeWidgetPrivate::GetWindowTitleFontList() {
 #if defined(OS_WIN)
   NONCLIENTMETRICS ncm;
   base::win::GetNonClientMetrics(&ncm);
   l10n_util::AdjustUIFont(&(ncm.lfCaptionFont));
   base::win::ScopedHFONT caption_font(CreateFontIndirect(&(ncm.lfCaptionFont)));
   return gfx::FontList(gfx::Font(caption_font));
 #else
   return gfx::FontList();
 #endif
 }
 
 }  // namespace internal
 }  // namespace views