Fix a long standing bug with the browser window losing focus when the user scrolled on the page usi…

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 ae24d047e5c7bb0e5f666297e1ad87242ec4625c..744b9eaddbc86a767316af0ed032e9b54c89fb33 100644
--- a/ui/views/win/hwnd_message_handler.cc
+++ b/ui/views/win/hwnd_message_handler.cc
@@ -1549,8 +1549,15 @@ LRESULT HWNDMessageHandler::OnMouseActivate(UINT message,
   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))
+  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