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

chrome/browser/notifications/balloon_collection_linux.cc

Index: chrome/browser/notifications/balloon_collection_linux.cc
diff --git a/chrome/browser/notifications/balloon_collection_linux.cc b/chrome/browser/notifications/balloon_collection_linux.cc
index 0255ae839faea607ff0d5ac29365da1b84ccb308..caf489c3fc1f4a276ad953dbee9bad66fb1a886c 100644
--- a/chrome/browser/notifications/balloon_collection_linux.cc
+++ b/chrome/browser/notifications/balloon_collection_linux.cc
@@ -39,6 +39,11 @@ void BalloonCollectionImpl::PositionBalloons(bool reposition) {
   PositionBalloonsInternal(reposition);
 }
 
+#if defined(TOUCH_UI) || defined(USE_AURA)
+void BalloonCollectionImpl::DidProcessEvent(const base::NativeEvent& event) {
+  NOTIMPLEMENTED();
+}
+#else
 void BalloonCollectionImpl::DidProcessEvent(GdkEvent* event) {
   switch (event->type) {
     case GDK_MOTION_NOTIFY:
@@ -49,6 +54,7 @@ void BalloonCollectionImpl::DidProcessEvent(GdkEvent* event) {
       break;
   }
 }
+#endif
 
 bool BalloonCollectionImpl::IsCursorInBalloonCollection() const {
   GdkScreen* screen = gdk_screen_get_default();