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
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index 0000000000000000000000000000000000000000..9619ceeda1250ee57085033816e75e532ae7fab0
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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 <jni.h>
+#include <vector>
+
+#include "base/android/scoped_java_ref.h"
+#include "base/macros.h"
+#include "base/strings/string16.h"
+#include "ui/events/events_export.h"
+#include "ui/gfx/geometry/point_conversions.h"
+
+namespace gfx {
+class PointF;
+}
+
+namespace ui {
+
+// Event class used to carry the info from Java DragEvent through native.
+// All coordinates are in DIPs.
+class EVENTS_EXPORT DragEventAndroid {
+ public:
+  DragEventAndroid(JNIEnv* env,
+                   int action,
+                   const gfx::PointF& location,
+                   const gfx::PointF& screen_location,
+                   const std::vector<base::string16>& mime_types,
+                   jstring content);
+  ~DragEventAndroid();
+
+  int action() const { return action_; }
+  const gfx::PointF& location_f() const { return location_; }
+  const gfx::PointF& screen_location_f() const { return screen_location_; }
+  const std::vector<base::string16>& mime_types() const { return mime_types_; }
+
+  const gfx::Point GetLocation() const;
+  const gfx::Point GetScreenLocation() const;
+  base::android::ScopedJavaLocalRef<jstring> GetJavaContent() const;
+
+  // Creates a new DragEventAndroid instance different from |this| only by
+  // its location.
+  std::unique_ptr<DragEventAndroid> CreateFor(
+      const gfx::PointF& new_location) const;
+
+ private:
+  int action_;
+  // Location relative to the view which the event is targeted.
+  gfx::PointF location_;
+  // Location relative to the screen coordinate.
+  gfx::PointF screen_location_;
+  const std::vector<base::string16>& mime_types_;
+  // The Java reference to the drop content to avoid unnecessary copying.
+  base::android::ScopedJavaGlobalRef<jstring> content_;
+
+  DISALLOW_COPY_AND_ASSIGN(DragEventAndroid);
+};
+
+}  // namespace ui
+
+#endif  // UI_EVENTS_ANDROID_DRAG_EVENT_ANDROID_H_