[Remoting Android] Refactor CursorShapeStubProxy from JniDisplayHandler

remoting/client/callback_cursor_shape_stub.h

+// Copyright 2016 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 REMOTING_CLIENT_CALLBACK_CURSOR_SHAPE_STUB_H_
+#define REMOTING_CLIENT_CALLBACK_CURSOR_SHAPE_STUB_H_
+
+#include "base/callback.h"
+#include "base/macros.h"
+#include "base/single_thread_task_runner.h"
+#include "remoting/protocol/cursor_shape_stub.h"
+
+namespace remoting {
+
+// A helper class for wrapping a cursor updating callback into a
+// CursorShapeStub. The callback will be run when SetCursorShape is called.

[Sergey Ulanov, 2016/07/27 18:26:09]

The comment doesn't mention that the callback is called on another thread.

[Yuwei, 2016/07/27 19:22:28]

Added comment.

+class CallbackCursorShapeStub : public protocol::CursorShapeStub {

[Sergey Ulanov, 2016/07/27 18:26:09]

In other places we call classes like this that move interface calls from on
thread to another a "proxy". So for consistency I think this should really be
called CursorShapeStubProxy and instead of taking a callback it should take a
CursorShapeStub (maybe WeakPtr<CursorShapeStub>). This also means that
Jni*DesktopHandler will need to implement CursorShapeStub.
This will also be useful if we needed to add other methods in that interface.

[Yuwei, 2016/07/27 18:37:20]

The class being proxied will need to implement the CursorShapeStub on display
thread, but It sounds like a CursorShapeStub should be run on the network
thread... This should work but may be slightly confusing?

[Sergey Ulanov, 2016/07/27 18:47:51]

There is no requirement that CursorShapeStub _interface_ is used on network
thread. But each implementation of that interface may require to be called on a
specific thread. JniDesktopHandler will implement CursorShapeStub and that
implementation will be called on desktop thread.

[Yuwei, 2016/07/27 19:22:28]

Done.

[Yuwei, 2016/07/27 19:22:28]

Acknowledged.

+ public:
+  // If |task_runner| is null, |callback| will be run upon the current call
+  // stack of SetCursorShape on the network thread. Otherwise it will be run
+  // on the thread of |task_runner|.
+  CallbackCursorShapeStub(
+      base::Callback<void(const protocol::CursorShapeInfo&)> callback,
+      scoped_refptr<base::SingleThreadTaskRunner> task_runner);
+  ~CallbackCursorShapeStub() override;
+
+  // CursorShapeStub override.
+  void SetCursorShape(const protocol::CursorShapeInfo& cursor_shape) override;
+
+ private:
+  base::Callback<void(const protocol::CursorShapeInfo&)> callback_;
+  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
+
+  DISALLOW_COPY_AND_ASSIGN(CallbackCursorShapeStub);
+};
+
+}  // namespace remoting
+
+#endif  // REMOTING_CLIENT_CALLBACK_CURSOR_SHAPE_STUB_H_