Don't do DefWindowProc on WM_NCACTIVATE if there's no frame.

ui/views/win/hwnd_message_handler.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/win/hwnd_message_handler.h"
 
 #include <dwmapi.h>
 #include <oleacc.h>
 #include <shellapi.h>
 #include <tchar.h>
@@ skipping 1801 matching lines @@
                  RDW_NOCHILDREN | RDW_INVALIDATE | RDW_UPDATENOW);
     EnumChildWindows(hwnd(), EnumChildWindowsForRedraw, NULL);
   }
 
   // The frame may need to redraw as a result of the activation change.
   // We can get WM_NCACTIVATE before we're actually visible. If we're not
   // visible, no need to paint.
   if (IsVisible())
     delegate_->SchedulePaint();
 
-  if (delegate_->GetFrameMode() == FrameMode::CUSTOM_DRAWN) {
+  // Calling DefWindowProc is only necessary if there's a system frame being
+  // drawn. Otherwise it can draw an incorrect title bar and cause visual
+  // corruption.
+  if (!delegate_->HasFrame() ||
+      delegate_->GetFrameMode() == FrameMode::CUSTOM_DRAWN) {
     SetMsgHandled(TRUE);
     return TRUE;
   }
 
   return DefWindowProcWithRedrawLock(
       WM_NCACTIVATE, render_as_active || active, 0);
 }
 
 LRESULT HWNDMessageHandler::OnNCCalcSize(BOOL mode, LPARAM l_param) {
   // We only override the default handling if we need to specify a custom
@@ skipping 1076 matching lines @@
   MONITORINFO monitor_info = {sizeof(monitor_info)};
   GetMonitorInfo(MonitorFromWindow(hwnd(), MONITOR_DEFAULTTOPRIMARY),
                  &monitor_info);
   gfx::Rect shrunk_rect(monitor_info.rcMonitor);
   shrunk_rect.set_height(shrunk_rect.height() - 1);
   background_fullscreen_hack_ = true;
   SetBoundsInternal(shrunk_rect, false);
 }
 
 }  // namespace views