Fix regions generation on windows.

chrome/browser/ui/views/panels/panel_frame_view.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 "chrome/browser/ui/views/panels/panel_frame_view.h"
 
 #include "chrome/browser/ui/panels/panel.h"
 #include "chrome/browser/ui/panels/panel_constants.h"
 #include "chrome/browser/ui/views/panels/panel_view.h"
 #include "chrome/browser/ui/views/tab_icon_view.h"
@@ skipping 337 matching lines @@
 
 #if defined(OS_WIN)
   // Changing the window region is going to force a paint. Only change the
   // window region if the region really differs.
   HWND native_window = views::HWNDForWidget(panel_view_->window());
   base::win::ScopedRegion current_region(::CreateRectRgn(0, 0, 0, 0));
   int current_region_result = ::GetWindowRgn(native_window, current_region);
 
   gfx::Path window_mask;
   GetWindowMask(size(), &window_mask);
-  base::win::ScopedRegion new_region(gfx::CreateHRGNFromSkPath(window_mask));
+  base::win::ScopedRegion new_region;
+  if (!window_mask.isEmpty())
+    new_region.Set(gfx::CreateHRGNFromSkPath(window_mask));
 
-  if (current_region_result == ERROR ||
-      !::EqualRgn(current_region, new_region)) {
+  const bool has_current_region = current_region != NULL;
+  const bool has_new_region = new_region != NULL;
+  if (has_current_region != has_new_region ||
+      (has_current_region && !::EqualRgn(current_region, new_region))) {
     // SetWindowRgn takes ownership of the new_region.
     ::SetWindowRgn(native_window, new_region.release(), TRUE);
   }
 #endif
 }
 
 gfx::Rect PanelFrameView::GetBoundsForClientView() const {
   // The origin of client-area bounds starts after left border and titlebar and
   // spans until hitting the right and bottom borders.
   //    +------------------------------+
@@ skipping 398 matching lines @@
 #endif
 }
 
 bool PanelFrameView::IsWithinResizingArea(
     const gfx::Point& mouse_location) const {
   panel::Resizability resizability = panel_view_->panel()->CanResizeByMouse();
   int edge_hittest = GetFrameEdgeHitTest(
       mouse_location, size(), PanelView::kResizeInsideBoundsSize, resizability);
   return edge_hittest != HTNOWHERE;
 }