Fix accessibility in Windows x64 build.

content/browser/renderer_host/legacy_render_widget_host_win.cc

Index: content/browser/renderer_host/legacy_render_widget_host_win.cc
diff --git a/content/browser/renderer_host/legacy_render_widget_host_win.cc b/content/browser/renderer_host/legacy_render_widget_host_win.cc
index 84d95aced8ba6c667138154caec7a8c9a6e2a6e5..10dcbce79f2b076108831a3eb790544b344e36fa 100644
--- a/content/browser/renderer_host/legacy_render_widget_host_win.cc
+++ b/content/browser/renderer_host/legacy_render_widget_host_win.cc
@@ -133,14 +133,17 @@ LRESULT LegacyRenderWidgetHostHWND::OnEraseBkGnd(UINT message,
 LRESULT LegacyRenderWidgetHostHWND::OnGetObject(UINT message,
                                                 WPARAM w_param,
                                                 LPARAM l_param) {
-  if (kIdScreenReaderHoneyPot == l_param) {
+  // Explicitly cast to DWORD for 64-bit support.
+  DWORD obj_id = static_cast<DWORD>(l_param);
+
+  if (kIdScreenReaderHoneyPot == obj_id) {
     // When an MSAA client has responded to our fake event on this id,
     // enable screen reader support.
     BrowserAccessibilityState::GetInstance()->OnScreenReaderDetected();
     return static_cast<LRESULT>(0L);
   }
 
-  if (OBJID_CLIENT != l_param || !manager_)
+  if (OBJID_CLIENT != obj_id || !manager_)
     return static_cast<LRESULT>(0L);
 
   base::win::ScopedComPtr<IAccessible> root(