Update window region after widget resizes not changing HWND size

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 <wtsapi32.h>
@@ skipping 507 matching lines @@
   if (show_state) {
     if (wp.showCmd == SW_SHOWMAXIMIZED)
       *show_state = ui::SHOW_STATE_MAXIMIZED;
     else if (wp.showCmd == SW_SHOWMINIMIZED)
       *show_state = ui::SHOW_STATE_MINIMIZED;
     else
       *show_state = ui::SHOW_STATE_NORMAL;
   }
 }
 
-void HWNDMessageHandler::SetBounds(const gfx::Rect& bounds_in_pixels) {
+void HWNDMessageHandler::SetBounds(const gfx::Rect& bounds_in_pixels,
+                                   bool force_size_changed) {
   LONG style = GetWindowLong(hwnd(), GWL_STYLE);
   if (style & WS_MAXIMIZE)
     SetWindowLong(hwnd(), GWL_STYLE, style & ~WS_MAXIMIZE);
+
+  gfx::Size old_size = GetClientAreaBounds().size();
   SetWindowPos(hwnd(), NULL, bounds_in_pixels.x(), bounds_in_pixels.y(),
                bounds_in_pixels.width(), bounds_in_pixels.height(),
                SWP_NOACTIVATE | SWP_NOZORDER);
+
+  // If HWND size is not changed, we will not receive standard size change
+  // notifications. If |force_size_changed| is |true|, we should pretend size is
+  // changed.
+  if (old_size == bounds_in_pixels.size() && force_size_changed) {
+    delegate_->HandleClientSizeChanged(GetClientAreaBounds().size());
+    ResetWindowRegion(false, true);
+  }
 }
 
 void HWNDMessageHandler::SetSize(const gfx::Size& size) {
   SetWindowPos(hwnd(), NULL, 0, 0, size.width(), size.height(),
                SWP_NOACTIVATE | SWP_NOZORDER | SWP_NOMOVE);
 }
 
 void HWNDMessageHandler::CenterWindow(const gfx::Size& size) {
   HWND parent = GetParent(hwnd());
   if (!IsWindow(hwnd()))
@@ skipping 1865 matching lines @@
     POINT cursor_pos = {0};
     ::GetCursorPos(&cursor_pos);
     if (memcmp(&cursor_pos, &mouse_location, sizeof(POINT)))
       return false;
     return true;
   }
   return false;
 }
 
 }  // namespace views