Create platform/mojo and move MojoHelper.h there

third_party/WebKit/Source/platform/MojoHelper.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 MojoHelper_h
-#define MojoHelper_h
-
-#include "base/bind.h"
-#include "mojo/public/cpp/bindings/callback.h"
-#include "mojo/public/cpp/bindings/wtf_array.h"
-#include "platform/heap/HeapAllocator.h"
-#include <utility>
-
-namespace blink {
-
-namespace internal {
-
-template <typename R, typename... Args>
-R CallWTFFunction(Function<R(Args...)>* functor, Args... args)
-{
-    return (*functor)(std::forward<Args>(args)...);
-}
-
-}
-
-// Binds an instance of a class to its member function. Does not bind anything
-// else. Provides limited access to base::Bind() function. base::Bind() could
-// be dangerous if it's used across threads, so we don't want to allow general
-// use of base::Bind(). See also "platform/ThreadSafeFunctional.h".
-template <typename Class, typename ReturnType, typename... Args>
-mojo::Callback<ReturnType(Args...)>
-sameThreadBindForMojo(ReturnType (Class::*method)(Args...), Class* instance)
-{
-    return base::Bind(method, base::Unretained(instance));
-}
-
-template <typename R, typename... Args>
-base::Callback<R(Args...)> createBaseCallback(PassOwnPtr<Function<R(Args...)>> functor)
-{
-    return base::Bind(&internal::CallWTFFunction<R, Args...>, base::Owned(functor.leakPtr()));
-}
-
-} // namespace blink
-
-namespace mojo {
-
-// A |TypeConverter| that will create a |WTFArray<T>| containing a copy of the
-// contents of a |blink::HeapVector<E>|, using |TypeConverter<T, E>| to copy
-// each element. The returned array will always be non-null.
-template <typename T, typename E>
-struct TypeConverter<WTFArray<T>, blink::HeapVector<E>> {
-    static WTFArray<T> Convert(const blink::HeapVector<E>& input)
-    {
-        WTFArray<T> result(input.size());
-        for (size_t i = 0; i < input.size(); ++i)
-            result[i] = TypeConverter<T, E>::Convert(input[i]);
-        return std::move(result);
-    }
-};
-
-} // namespace mojo
-
-#endif // MojoHelper_h