content: Add ContextProviderFactory to create a render ContextProvider.

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