Allow std::unordered_*.

gpu/command_buffer/service/framebuffer_completeness_cache.h

 // Copyright 2015 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 GPU_COMMAND_BUFFER_SERVICE_FRAMEBUFFER_COMPLETENESS_CACHE_H_
 #define GPU_COMMAND_BUFFER_SERVICE_FRAMEBUFFER_COMPLETENESS_CACHE_H_
 
+#include <string>
+
 #include "base/containers/hash_tables.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "gpu/gpu_export.h"
 
 namespace gpu {
 namespace gles2 {
 
 // Refcounted wrapper for a hash_set of framebuffer format signatures
 // representing framebuffer configurations that are reported by the GL
@@ skipping 16 matching lines @@
 
   Map cache_;
 
   DISALLOW_COPY_AND_ASSIGN(FramebufferCompletenessCache);
 };
 
 }  // namespace gles2
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_SERVICE_FRAMEBUFFER_COMPLETENESS_CACHE_H_