Consolidate Widget Event code, other cleanup.

views/widget/native_widget_delegate.h

Index: views/widget/native_widget_delegate.h
diff --git a/views/widget/native_widget_delegate.h b/views/widget/native_widget_delegate.h
index 26e4828d4f9a648e126a0e70c3c504d8343c5ea6..e5e3752a696372902af269b88cadce9d40614629 100644
--- a/views/widget/native_widget_delegate.h
+++ b/views/widget/native_widget_delegate.h
@@ -40,6 +40,10 @@ class NativeWidgetDelegate {
   // Paints the rootview in the canvas. This will also refresh the compositor
   // tree if necessary when accelerated painting is enabled.
   virtual void OnNativeWidgetPaint(gfx::Canvas* canvas) = 0;
+
+  // MouseEvent handlers.
+  virtual bool OnMouseEvent(const MouseEvent& event) = 0;
+  virtual void OnMouseCaptureLost() = 0;
 };
 
 }  // namespace internal