Introduce ViewRoot forwarding input/view events to native

ui/android/view_root.h

+// Copyright 2016 The Chromium Authors. All rights reserved.

[boliu, 2017/01/03 19:16:11]

new year!

[Jinsuk Kim, 2017/01/04 10:45:02]

Done.

+// 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 <string>
+#include <vector>
+
+#include "base/android/jni_weak_ref.h"
+#include "base/android/scoped_java_ref.h"
+#include "base/macros.h"
+#include "base/time/time.h"
+#include "ui/android/ui_android_export.h"
+#include "ui/android/view_android.h"
+#include "ui/gfx/geometry/vector2d_f.h"
+
+namespace ui {
+
+// ViewRoot is the root of a ViewAndroid tree.
+class UI_ANDROID_EXPORT ViewRoot : public ViewAndroid {
+ public:
+  ViewRoot();

[boliu, 2017/01/03 19:16:11]

Instead of this, have a "CreateForTesting" method, that also creates the java
part as well. See WindowAndroid::CreateForTesting for example.

[Jinsuk Kim, 2017/01/04 10:45:02]

It's also used in blimp. Replaced it with ViewRoot(WindowAndroid*).

+  ViewRoot(JNIEnv* env,
+           const base::android::JavaParamRef<jobject>& obj,
+           jlong jwindow_android);
+
+  ~ViewRoot() override;
+
+  // ViewAndroid overrides.
+  WindowAndroid* GetWindowAndroid() const override;
+  void SetWindowAndroid(WindowAndroid* window) override;
+
+  static ViewRoot* FromJavaObject(JNIEnv* env,
+      const base::android::JavaParamRef<jobject>& obj);

[boliu, 2017/01/03 19:16:11]

nit: indent is wrong here and below

[Jinsuk Kim, 2017/01/04 10:45:02]

Done.

+  void OnPhysicalBackingSizeChanged(JNIEnv* env,
+    const base::android::JavaParamRef<jobject>& jobj,
+    int width,
+    int height);
+
+ private:
+  // ViewAndroid overrides.
+  ViewAndroid* GetViewRoot() override;
+
+  JavaObjectWeakGlobalRef java_obj_;

[boliu, 2017/01/03 19:16:11]

only looking at ui/ code right now, and it's not clear to me what the ownership
relationship is between native and java ViewRoot. eg what's responsible for
deleting the native side?

And whatever the ownership relationship is (other than relying on gc), this can
be a strong reference.

[Jinsuk Kim, 2017/01/04 10:45:02]

Updated to destroy the native side when all of its children are removed.
ViewRoot always starts with adding one child, so the destruction gets triggered
when the associated web content is destroyed.
Any suggestion to avoid potential issue is welcome. I don't have a good idea...
now its use is limited to accessing a single call to Java (onDestroyNativeView).

[boliu, 2017/01/04 17:45:10]

That seems wrong for chrome, where we expect the ViewRoot to stay even after all
the tabs are closed? Probably should just make it like WindowAndroid, have an
explicit destroy method on java that cleans up the native side.
Using a strong ref here is ok.

[Jinsuk Kim, 2017/01/05 11:03:12]

Done.
Now that onDestroyNative is gone, java obj is not needed any more atm.

+  WindowAndroid* window_;
+
+  DISALLOW_COPY_AND_ASSIGN(ViewRoot);
+};
+
+bool RegisterViewRoot(JNIEnv* env);
+
+}  // namespace ui
+
+#endif  // UI_ANDROID_VIEW_ROOT_H_