Force a frame changed message (WM_NCCALCSIZE) to occur during settings change.

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 1312 matching lines @@
 }
 
 void HWNDMessageHandler::OnDestroy() {
   windows_session_change_observer_.reset(nullptr);
   delegate_->HandleDestroying();
 }
 
 void HWNDMessageHandler::OnDisplayChange(UINT bits_per_pixel,
                                          const gfx::Size& screen_size) {
   delegate_->HandleDisplayChange();
+  // Force a WM_NCCALCSIZE to occur to ensure that we handle auto hide
+  // taskbars correctly.
   SendFrameChanged();
 }
 
 LRESULT HWNDMessageHandler::OnDwmCompositionChanged(UINT msg,
                                                     WPARAM w_param,
                                                     LPARAM l_param) {
   if (!delegate_->IsWidgetWindow()) {
     SetMsgHandled(FALSE);
     return 0;
   }
@@ skipping 638 matching lines @@
     // Fire a dummy SetWindowPos() call, so we'll trip the code in
     // OnWindowPosChanging() below that notices work area changes.
     ::SetWindowPos(hwnd(), 0, 0, 0, 0, 0, SWP_NOSIZE | SWP_NOMOVE |
         SWP_NOZORDER | SWP_NOREDRAW | SWP_NOACTIVATE | SWP_NOOWNERZORDER);
     SetMsgHandled(TRUE);
   } else {
     if (flags == SPI_SETWORKAREA)
       delegate_->HandleWorkAreaChanged();
     SetMsgHandled(FALSE);
   }
+
+  // If the work area is changing, then it could be as a result of the taskbar
+  // broadcasting the WM_SETTINGCHANGE message due to changes in auto hide
+  // settings, etc. Force a WM_NCCALCSIZE to occur to ensure that we handle
+  // this correctly.
+  if (flags == SPI_SETWORKAREA)
+    SendFrameChanged();
 }
 
 void HWNDMessageHandler::OnSize(UINT param, const gfx::Size& size) {
   RedrawWindow(hwnd(), NULL, NULL, RDW_INVALIDATE | RDW_ALLCHILDREN);
   // ResetWindowRegion is going to trigger WM_NCPAINT. By doing it after we've
   // invoked OnSize we ensure the RootView has been laid out.
   ResetWindowRegion(false, true);
 
   // We add the WS_VSCROLL and WS_HSCROLL styles to top level windows to ensure
   // that legacy trackpad/trackpoint drivers generate the WM_VSCROLL and
@@ skipping 571 matching lines @@
 
     default:
       left_button_down_on_caption_ = false;
       break;
   }
   return handled;
 }
 
 
 }  // namespace views