ViewRoot class for event forwarding on Android

ui/android/view_root.h

+// 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_ANDROID_VIEW_ROOT_H_
+#define UI_ANDROID_VIEW_ROOT_H_
+
+#include <jni.h>
+
+#include "base/android/scoped_java_ref.h"
+#include "ui/android/ui_android_export.h"
+#include "ui/android/view_android.h"
+
+namespace ui {
+
+// ViewRoot is the root of a ViewAndroid tree.
+class UI_ANDROID_EXPORT ViewRoot : public ViewAndroid {
+ public:
+  explicit ViewRoot(jlong window_android_ptr);
+
+  void Destroy(JNIEnv* env,
+               const base::android::JavaParamRef<jobject>& obj);
+
+  // ViewAndroid overrides.
+  WindowAndroid* GetWindowAndroid() const override;
+  ViewAndroid* GetViewRoot() override;
+
+  // Move the give child ViewAndroid to the front of the list
+  // so that it can be the first responder of events.
+  void MoveToFront(ViewAndroid* child);

[boliu, 2017/01/24 23:47:13]

why only on the root?

[Jinsuk Kim, 2017/01/25 02:34:34]

Practically this is necessary only at the top level to decide which web content
the event should be routed to. I can make it general and put it in ViewAndroid. 
But not sure what it means to have more than one child(RWHVA) below it at the
same time and switching their order in the view list...?

[Jinsuk Kim, 2017/01/25 08:13:31]

On second thought, this should be in ViewAndroid. Will move it in the next
patch.

+
+  jboolean OnTouchEvent(
+      JNIEnv* env,
+      const base::android::JavaParamRef<jobject>& obj,
+      const base::android::JavaParamRef<jobject>& motion_event,
+      jlong time_ms,
+      jint android_action,
+      jint pointer_count,
+      jint history_size,
+      jint action_index,
+      jfloat pos_x_0,
+      jfloat pos_y_0,
+      jfloat pos_x_1,
+      jfloat pos_y_1,
+      jint pointer_id_0,
+      jint pointer_id_1,
+      jfloat touch_major_0,
+      jfloat touch_major_1,
+      jfloat touch_minor_0,
+      jfloat touch_minor_1,
+      jfloat orientation_0,
+      jfloat orientation_1,
+      jfloat tilt_0,
+      jfloat tilt_1,
+      jfloat raw_pos_x,
+      jfloat raw_pos_y,
+      jint android_tool_type_0,
+      jint android_tool_type_1,
+      jint android_button_state,
+      jint android_meta_state,
+      jboolean is_touch_handle_event);
+
+ private:
+  WindowAndroid* window_;
+
+  DISALLOW_COPY_AND_ASSIGN(ViewRoot);
+};
+
+bool RegisterViewRoot(JNIEnv* env);
+
+}  // namespace ui
+
+#endif  // UI_ANDROID_VIEW_ROOT_H_