Remove unused include in sequenced_worker_pool.h

cc/output/context_cache_controller.h

 // Copyright (c) 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 CC_OUTPUT_CONTEXT_CACHE_CONTROLLER_H_
 #define CC_OUTPUT_CONTEXT_CACHE_CONTROLLER_H_
 
 #include <cstdint>
 #include <memory>
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
+#include "base/single_thread_task_runner.h"
 #include "cc/base/cc_export.h"
 
 class GrContext;
 
 namespace base {
 class Lock;
-class SingleThreadTaskRunner;
 }
 
 namespace gpu {
 class ContextSupport;
 }
 
 namespace cc {
 
 // ContextCacheController manages clearing cached data on ContextProvider when
 // appropriate. Currently, cache clearing is triggered when the Context
@@ skipping 70 matching lines @@
   base::Lock current_idle_generation_lock_;
   uint32_t current_idle_generation_ = 0;
 
   base::WeakPtr<ContextCacheController> weak_ptr_;
   base::WeakPtrFactory<ContextCacheController> weak_factory_;
 };
 
 }  // namespace cc
 
 #endif  // CC_OUTPUT_CONTEXT_CACHE_CONTROLLER_H_