Route OnDragEvent through ViewAndroid tree

ui/events/android/drag_event_android.h

Index: ui/events/android/drag_event_android.h
diff --git a/ui/events/android/drag_event_android.h b/ui/events/android/drag_event_android.h
new file mode 100644
index 0000000000000000000000000000000000000000..52b515c40337837197b05f4e93fbb4799b49d088
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+++ b/ui/events/android/drag_event_android.h
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+// Copyright 2017 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.
+
+#ifndef UI_EVENTS_ANDROID_DRAG_EVENT_ANDROID_H_
+#define UI_EVENTS_ANDROID_DRAG_EVENT_ANDROID_H_
+
+#include "ui/events/event.h"
+#include "ui/events/events_export.h"
+
+namespace gfx {
+class Point;
+}
+
+namespace ui {
+
+// Implementation of ui::LocatedEvent wrapping a native Android DragEvent.
+// All coordinates are in DIPs.
+class EVENTS_EXPORT DragEventAndroid : public LocatedEvent {
+ public:
+  DragEventAndroid(int action,
+                   const gfx::PointF& location,
+                   const gfx::PointF& screen_location,
+                   const std::vector<base::string16>& mime_types,
+                   const base::string16& content);
+  int action() const { return action_; }
+  const std::vector<base::string16>& mime_types() const { return mime_types_; }
+  const base::string16& content() const { return content_; }
+
+  // Creates a new DragEventAndroid instance different from |this| only by
+  // its location.
+  std::unique_ptr<DragEventAndroid> CreateFor(const gfx::Point& location) const;
+
+ private:
+  int action_;
+  const std::vector<base::string16>& mime_types_;
+  const base::string16& content_;
+
+  DISALLOW_COPY_AND_ASSIGN(DragEventAndroid);
+};
+
+}  // namespace ui
+
+#endif  // UI_EVENTS_ANDROID_DRAG_EVENT_ANDROID_H_