DialogSurfaceManager implementation.

media/base/android/dialog_surface_callback.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 MEDIA_BASE_ANDROID_DIALOG_SURFACE_CALLBACK_H_
+#define MEDIA_BASE_ANDROID_DIALOG_SURFACE_CALLBACK_H_
+
+#include <jni.h>
+#include <stddef.h>
+#include <stdint.h>
+
+#include <set>
+#include <string>
+
+#include "base/android/scoped_java_ref.h"
+#include "base/lazy_instance.h"
+#include "base/macros.h"
+#include "base/single_thread_task_runner.h"
+#include "base/task_runner.h"
+#include "base/threading/thread_checker.h"
+#include "base/time/time.h"
+#include "media/base/android/dialog_surface.h"
+#include "media/base/media_export.h"
+#include "ui/gfx/geometry/point.h"
+#include "ui/gfx/geometry/size.h"
+
+namespace base {
+class WaitableEvent;
+}
+
+namespace media {
+
+// This class implements the C++ wrapper around the java DialogSurfaceCallback.
+// Callbacks will happen on the thread that it's created on.
+// It handles threading and object lifecycle issues.  In particular, it's safe
+// to delete this object on the same thread as it was created on at any time,
+// even during a callback.  Future callbacks from java will be cancelled
+// automatically, regardless of java threading.
+class MEDIA_EXPORT DialogSurfaceCallback {
+ public:
+  // |callback| will be called on the same thread that we're created on,
+  // regardless of the thread that's used to call from java.
+  DialogSurfaceCallback(const DialogSurface::Callback& callback);

[boliu, 2017/01/04 01:48:44]

explicit

[liberato (no reviews please), 2017/01/11 22:17:57]

Done.

+  ~DialogSurfaceCallback();
+
+  // Callback that we should use to send the java surface when it arrives.
+  using AndroidSurfaceCB =
+      base::Callback<void(const base::android::JavaRef<jobject>& jsurface)>;
+
+  // Sets the callback that we'll use to provide the surface to DialogSurface.
+  void SetAndroidSurfaceCB(const AndroidSurfaceCB& cb);
+
+  scoped_refptr<base::SingleThreadTaskRunner> GetTaskRunner() const;
+  bool CalledOnValidThread() const;
+
+  jobject obj() const { return j_surface_callback_.obj(); }

[boliu, 2017/01/04 01:48:44]

hmm, having an obj() method is generally a red flag that it's a class is
unnecessarily exposing internals

I don't have any good ideas for avoiding this one though, but something to think
about..

[liberato (no reviews please), 2017/01/11 22:17:56]

Acknowledged.

+
+  // Called on the proper thread for the callback for |id|, though |id| might
+  // no longer refer to a valid callback.  |jsurface_opt| is an optional object
+  // that goes with the callback.  For OP_CREATED, it is the Android Surface.
+  static void OnCallbackProperThread(
+      long id,
+      DialogSurface::CallbackOp what,
+      base::android::ScopedJavaGlobalRef<jobject> jobject_opt,
+      base::WaitableEvent* event);
+
+  static bool RegisterDialogSurfaceCallback(JNIEnv* env);
+
+ private:
+  // Java callback instance.
+  base::android::ScopedJavaGlobalRef<jobject> j_surface_callback_;
+
+  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
+
+  // |id_| must be non-repeating.  We can't use |this| directly because of race
+  // conditions with destruction and re-allocation.
+  long id_;
+
+  DialogSurface::Callback callback_;
+
+  base::ThreadChecker thread_checker_;
+
+  AndroidSurfaceCB android_surface_cb_;
+
+  DISALLOW_COPY_AND_ASSIGN(DialogSurfaceCallback);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_BASE_ANDROID_DIALOG_SURFACE_CALLBACK_H_