Remove code for losing activation when child window activated.

ui/views/win/hwnd_message_handler.cc

Index: ui/views/win/hwnd_message_handler.cc
diff --git a/ui/views/win/hwnd_message_handler.cc b/ui/views/win/hwnd_message_handler.cc
index 0cacffe4a76dfdde167943bf1f232f87736b9a76..f28f1dcfbb741d1333da57dc4066f796964153ca 100644
--- a/ui/views/win/hwnd_message_handler.cc
+++ b/ui/views/win/hwnd_message_handler.cc
@@ -1519,20 +1519,6 @@ LRESULT HWNDMessageHandler::OnMouseActivate(UINT message,
     ::RemoveProp(hwnd(), ui::kIgnoreTouchMouseActivateForWindow);
     return MA_NOACTIVATE;
   }
-  // A child window activation should be treated as if we lost activation.
-  POINT cursor_pos = {0};
-  ::GetCursorPos(&cursor_pos);
-  ::ScreenToClient(hwnd(), &cursor_pos);
-  // The code below exists for child windows like NPAPI plugins etc which need
-  // to be activated whenever we receive a WM_MOUSEACTIVATE message. Don't put
-  // transparent child windows in this bucket as they are not supposed to grab
-  // activation.
-  // TODO(ananta)
-  // Get rid of this code when we deprecate NPAPI plugins.
-  HWND child = ::RealChildWindowFromPoint(hwnd(), cursor_pos);
-  if (::IsWindow(child) && child != hwnd() && ::IsWindowVisible(child) &&
-      !(::GetWindowLong(child, GWL_EXSTYLE) & WS_EX_TRANSPARENT))
-    PostProcessActivateMessage(WA_INACTIVE, false);
 
   // TODO(beng): resolve this with the GetWindowLong() check on the subsequent
   //             line.