content/ui[Android]: Remove ContextProviderFactory.

ui/android/context_provider_factory.cc

-// 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.
-
-#include "ui/android/context_provider_factory.h"
-
-#include "cc/output/context_provider.h"
-
-namespace ui {
-namespace {
-
-ContextProviderFactory* g_context_provider_factory = nullptr;
-
-}  // namespace
-
-// static
-ContextProviderFactory* ContextProviderFactory::GetInstance() {
-  return g_context_provider_factory;
-}
-
-// static
-void ContextProviderFactory::SetInstance(
-    ContextProviderFactory* context_provider_factory) {
-  DCHECK(!g_context_provider_factory || !context_provider_factory);
-
-  g_context_provider_factory = context_provider_factory;
-}
-
-}  // namespace ui