Use GpuPreferences to avoid directly accessing switches in gpu related code

gpu/command_buffer/service/memory_program_cache.h

 // Copyright (c) 2012 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_MEMORY_PROGRAM_CACHE_H_
 #define GPU_COMMAND_BUFFER_SERVICE_MEMORY_PROGRAM_CACHE_H_
 
 #include <stddef.h>
 
 #include <map>
 #include <string>
 
 #include "base/containers/hash_tables.h"
 #include "base/containers/mru_cache.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "gpu/command_buffer/service/gles2_cmd_decoder.h"
 #include "gpu/command_buffer/service/program_cache.h"
 
 namespace gpu {
+
+struct GpuPreferences;
+
 namespace gles2 {
 
 // Program cache that stores binaries completely in-memory
 class GPU_EXPORT MemoryProgramCache : public ProgramCache {
  public:
-  MemoryProgramCache();
-  explicit MemoryProgramCache(const size_t max_cache_size_bytes);
+  MemoryProgramCache(size_t max_cache_size_bytes,
+                     bool disable_gpu_shader_disk_cache);
   ~MemoryProgramCache() override;
 
   ProgramLoadResult LoadLinkedProgram(
       GLuint program,
       Shader* shader_a,
       Shader* shader_b,
       const LocationMap* bind_attrib_location_map,
       const std::vector<std::string>& transform_feedback_varyings,
       GLenum transform_feedback_buffer_mode,
       const ShaderCacheCallback& shader_callback) override;
@@ skipping 104 matching lines @@
 
     DISALLOW_COPY_AND_ASSIGN(ProgramCacheValue);
   };
 
   friend class ProgramCacheValue;
 
   typedef base::MRUCache<std::string,
                          scoped_refptr<ProgramCacheValue> > ProgramMRUCache;
 
   const size_t max_size_bytes_;
+  const bool disable_gpu_shader_disk_cache_;
   size_t curr_size_bytes_;
   ProgramMRUCache store_;
 
   DISALLOW_COPY_AND_ASSIGN(MemoryProgramCache);
 };
 
 }  // namespace gles2
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_SERVICE_MEMORY_PROGRAM_CACHE_H_