Route OnDragEvent through ViewAndroid tree

ui/events/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//testing/test.gni")
 import("//ui/base/ui_features.gni")
 import("//ui/ozone/ozone.gni")
 
@@ skipping 182 matching lines @@
       "gestures/motion_event_aura.h",
     ]
   }
 
   if (is_win || is_mac || use_x11 || use_ozone || (is_android && use_aura)) {
     sources -= [ "events_stub.cc" ]
   }
 
   if (is_android) {
     sources += [
+      "android/drag_event_android.cc",
+      "android/drag_event_android.h",
       "android/key_event_utils.cc",
       "android/key_event_utils.h",
       "android/motion_event_android.cc",
       "android/motion_event_android.h",
     ]
     deps += [
       ":keyevent_jni_headers",
       ":motionevent_jni_headers",
     ]
   }
@@ skipping 286 matching lines @@
   generate_jar_jni("motionevent_jni_headers") {
     jni_package = "ui"
     classes = [ "android/view/MotionEvent.class" ]
   }
 
   generate_jar_jni("keyevent_jni_headers") {
     jni_package = "ui"
     classes = [ "android/view/KeyEvent.class" ]
   }
 }