Makes NativeViewHostWin change the parent of the hwnd when

ui/base/win/hidden_window.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/base/win/hidden_window.h"
+
+#include "ui/base/win/window_impl.h"
+
+namespace ui {
+
+namespace {
+
+// We need to have a parent window for the compositing code to work correctly.
+//
+// A tab will not have a parent HWND whenever it is not active in its
+// host window - for example at creation time and when it's in the
+// background, so we provide a default widget to host them.
+//
+// It may be tempting to use GetDesktopWindow() instead, but this is
+// problematic as the shell sends messages to children of the desktop
+// window that interact poorly with us.
+//
+// See: http://crbug.com/16476
+class TempParent : public ui::WindowImpl {
+ public:
+  static TempParent* Get() {
+    static TempParent* g_temp_parent;
+    if (!g_temp_parent) {
+      g_temp_parent = new TempParent();
+
+      g_temp_parent->set_window_style(WS_POPUP);
+      g_temp_parent->set_window_ex_style(WS_EX_TOOLWINDOW);
+      g_temp_parent->Init(GetDesktopWindow(), gfx::Rect());
+      EnableWindow(g_temp_parent->hwnd(), FALSE);
+    }
+    return g_temp_parent;
+  }
+
+ private:
+  // Explicitly do nothing in Close. We do this as some external apps may get a
+  // handle to this window and attempt to close it.
+  void OnClose() {
+  }
+
+  BEGIN_MSG_MAP_EX(WebContentsViewWin)
+    MSG_WM_CLOSE(OnClose)
+  END_MSG_MAP()
+};
+
+}  // namespace
+
+HWND GetHiddenWindow() {
+  return TempParent::Get()->hwnd();
+}
+
+}  // namespace ui