Ensure LegacyRenderWidgetHostHWND is always created.

content/browser/renderer_host/render_widget_host_view_aura.h

Index: content/browser/renderer_host/render_widget_host_view_aura.h
diff --git a/content/browser/renderer_host/render_widget_host_view_aura.h b/content/browser/renderer_host/render_widget_host_view_aura.h
index 51942cd96d961b17e3b8be7071351206533562de..8a5aa7fb398e69f1000497b7d5c43c8a6342aea1 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.h
+++ b/content/browser/renderer_host/render_widget_host_view_aura.h
@@ -391,6 +391,11 @@ class CONTENT_EXPORT RenderWidgetHostViewAura
   void InternalSetBounds(const gfx::Rect& rect);
 
 #if defined(OS_WIN)
+  // Create and/or update the legacy dummy window which corresponds to
+  // the bounds of the webcontents. It is needed for accessibility and
+  // for scrolling to work in legacy drivers for trackpoints/trackpads, etc.
+  void UpdateLegacyWin();
+
   bool UsesNativeWindowFrame() const;
 #endif