Move BindToCurrentLoop from media/base/ to base/

media/base/bind_to_current_loop.h

-// Copyright (c) 2015 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_BIND_TO_CURRENT_LOOP_H_
-#define MEDIA_BASE_BIND_TO_CURRENT_LOOP_H_
-
-#include "base/bind.h"
-#include "base/location.h"
-#include "base/message_loop/message_loop_proxy.h"
-#include "base/single_thread_task_runner.h"
-
-// This is a helper utility for base::Bind()ing callbacks to the current
-// MessageLoop. The typical use is when |a| (of class |A|) wants to hand a
-// callback such as base::Bind(&A::AMethod, a) to |b|, but needs to ensure that
-// when |b| executes the callback, it does so on |a|'s current MessageLoop.
-//
-// Typical usage: request to be called back on the current thread:
-// other->StartAsyncProcessAndCallMeBack(
-//    media::BindToCurrentLoop(base::Bind(&MyClass::MyMethod, this)));
-//
-// Note that like base::Bind(), BindToCurrentLoop() can't bind non-constant
-// references, and that *unlike* base::Bind(), BindToCurrentLoop() makes copies
-// of its arguments, and thus can't be used with arrays.
-
-namespace media {
-
-// Mimic base::internal::CallbackForward, replacing p.Pass() with
-// base::Passed(&p) to account for the extra layer of indirection.
-namespace internal {
-template <typename T>
-T& TrampolineForward(T& t) { return t; }
-
-template <typename T, typename R>
-base::internal::PassedWrapper<scoped_ptr<T, R> > TrampolineForward(
-    scoped_ptr<T, R>& p) { return base::Passed(&p); }
-
-template <typename T>
-base::internal::PassedWrapper<ScopedVector<T> > TrampolineForward(
-    ScopedVector<T>& p) { return base::Passed(&p); }
-
-// First, tell the compiler TrampolineHelper is a struct template with one
-// type parameter.  Then define specializations where the type is a function
-// returning void and taking zero or more arguments.
-template <typename Sig> struct TrampolineHelper;
-
-template <typename... Args>
-struct TrampolineHelper<void(Args...)> {
-  static void Run(
-      const scoped_refptr<base::SingleThreadTaskRunner>& task_runner,
-      const base::Callback<void(Args...)>& cb,
-      Args... args) {
-    task_runner->PostTask(FROM_HERE,
-                          base::Bind(cb, TrampolineForward(args)...));
-  }
-};
-
-}  // namespace internal
-
-template<typename T>
-static base::Callback<T> BindToCurrentLoop(
-    const base::Callback<T>& cb) {
-  return base::Bind(&internal::TrampolineHelper<T>::Run,
-                    base::MessageLoopProxy::current(), cb);
-}
-
-}  // namespace media
-
-#endif  // MEDIA_BASE_BIND_TO_CURRENT_LOOP_H_