Route OnDragEvent through ViewAndroid tree

ui/android/event_forwarder.h

Index: ui/android/event_forwarder.h
diff --git a/ui/android/event_forwarder.h b/ui/android/event_forwarder.h
index 480ec265538f55ca4bb60cf5151671b47cc5b3ec..ddc02b9f18df4c5edd446d99667c4edadc1e783c 100644
--- a/ui/android/event_forwarder.h
+++ b/ui/android/event_forwarder.h
@@ -70,6 +70,16 @@ class EventForwarder {
                          jfloat ticks_y,
                          jfloat pixels_per_tick);
 
+  void OnDragEvent(JNIEnv* env,
+                   const base::android::JavaParamRef<jobject>& jobj,
+                   jint action,
+                   jint x,
+                   jint y,
+                   jint screen_x,
+                   jint screen_y,
+                   const base::android::JavaParamRef<jobjectArray>& j_mimeTypes,
+                   const base::android::JavaParamRef<jstring>& j_content);
+
  private:
   friend class ViewAndroid;