Consolidate message observer API for win and aura (and touch).

views/widget/native_widget_gtk.cc

Index: views/widget/native_widget_gtk.cc
diff --git a/views/widget/native_widget_gtk.cc b/views/widget/native_widget_gtk.cc
index b6a228055f56d16b8a04bfcacf7a384a1601c2fd..fbb823507eb03e1d9828e752fe8ba9cdd222a687 100644
--- a/views/widget/native_widget_gtk.cc
+++ b/views/widget/native_widget_gtk.cc
@@ -260,7 +260,15 @@ class NativeWidgetGtk::DropObserver : public MessageLoopForUI::Observer {
   static DropObserver* GetInstance() {
     return Singleton<DropObserver>::get();
   }
+#if defined(TOUCH_UI)
+  virtual base::EventStatus WillProcessEvent(
+      const base::NativeEvent& event) OVERRIDE {
+    return base::EVENT_CONTINUE;
+  }
 
+  virtual void DidProcessEvent(const base::NativeEvent& event) OVERRIDE {
+  }
+#else
   virtual void WillProcessEvent(GdkEvent* event) {
     if (event->type == GDK_DROP_START) {
       NativeWidgetGtk* widget = GetNativeWidgetGtkForEvent(event);
@@ -271,6 +279,7 @@ class NativeWidgetGtk::DropObserver : public MessageLoopForUI::Observer {
 
   virtual void DidProcessEvent(GdkEvent* event) {
   }
+#endif
 
  private:
   NativeWidgetGtk* GetNativeWidgetGtkForEvent(GdkEvent* event) {