Add NPChannelBase::GetModalDialogEvent() to avoid content/plugin/ include from npobject_proxy.cc

content/common/np_channel_base.cc

Index: content/common/np_channel_base.cc
diff --git a/content/common/np_channel_base.cc b/content/common/np_channel_base.cc
index e5f8f02b3baafdf202bbbff803c2e6bea2aaf060..4c2b542a5bcb47938c17c3aedee635487fb9c350 100644
--- a/content/common/np_channel_base.cc
+++ b/content/common/np_channel_base.cc
@@ -110,6 +110,11 @@ NPObjectBase* NPChannelBase::GetNPObjectListenerForRoute(int route_id) {
   return iter->second;
 }
 
+base::WaitableEvent* NPChannelBase::GetModalDialogEvent(
+    gfx::NativeViewId containing_window) {
+  return NULL;
+}
+
 bool NPChannelBase::Init(base::MessageLoopProxy* ipc_message_loop,
                          bool create_pipe_now,
                          base::WaitableEvent* shutdown_event) {