content: Move shader cache factory singleton into a separate file.

content/browser/gpu/shader_cache_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 "content/browser/gpu/shader_cache_factory.h"
+
+#include "base/single_thread_task_runner.h"
+#include "content/browser/gpu/shader_disk_cache.h"
+
+namespace content {
+
+namespace {
+
+ShaderCacheFactory* factory_instance = nullptr;
+
+void CreateFactoryInstance(
+    scoped_refptr<base::SingleThreadTaskRunner> cache_task_runner) {
+  DCHECK(!factory_instance);
+  factory_instance = new ShaderCacheFactory(std::move(cache_task_runner));
+}
+
+}  // namespace
+
+void InitShaderCacheFactorySingleton(
+    scoped_refptr<base::SingleThreadTaskRunner> task_runner,
+    scoped_refptr<base::SingleThreadTaskRunner> cache_task_runner) {
+  if (task_runner->BelongsToCurrentThread()) {
+    CreateFactoryInstance(std::move(cache_task_runner));
+  } else {
+    task_runner->PostTask(FROM_HERE, base::Bind(&CreateFactoryInstance,
+                                                std::move(cache_task_runner)));
+  }
+}
+
+ShaderCacheFactory* GetShaderCacheFactorySingleton() {
+  DCHECK(!factory_instance || factory_instance->CalledOnValidThread());
+  return factory_instance;
+}
+
+}  // namespace content