Make ShaderTranslatorCache thread safe

gpu/command_buffer/service/shader_translator_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_SHADER_TRANSLATOR_CACHE_H_
 #define GPU_COMMAND_BUFFER_SERVICE_SHADER_TRANSLATOR_CACHE_H_
 
 #include <string.h>
 
 #include <map>
 
 #include "base/memory/ref_counted.h"
-#include "base/memory/singleton.h"
 #include "gpu/command_buffer/service/shader_translator.h"
 #include "third_party/angle/include/GLSLANG/ShaderLang.h"
 
 namespace gpu {
 namespace gles2 {
 
-// This singleton and the cache that it implements is NOT thread safe.
-// We're relying on the fact that the all GLES2DecoderImpl's are used
-// on one thread.
+// This class is not thread safe and can only be created and destroyed
+// on a single thread. But it is safe to use two independent instances on two
+// threads without synchronization.
 //
 // TODO(backer): Investigate using glReleaseShaderCompiler as an alternative to
 // to this cache.
-class ShaderTranslatorCache : public ShaderTranslator::DestructionObserver {
+class GPU_EXPORT ShaderTranslatorCache
+    : public base::RefCounted<ShaderTranslatorCache>,
+      public NON_EXPORTED_BASE(ShaderTranslator::DestructionObserver) {
  public:
-  static ShaderTranslatorCache* GetInstance();
+  ShaderTranslatorCache();
 
   // ShaderTranslator::DestructionObserver implementation
   virtual void OnDestruct(ShaderTranslator* translator) OVERRIDE;
 
   scoped_refptr<ShaderTranslator> GetTranslator(
       ShShaderType shader_type,
       ShShaderSpec shader_spec,
       const ShBuiltInResources* resources,
       ShaderTranslatorInterface::GlslImplementationType
           glsl_implementation_type,
       ShCompileOptions driver_bug_workarounds);
 
  private:
-  ShaderTranslatorCache();
+  friend class base::RefCounted<ShaderTranslatorCache>;
   virtual ~ShaderTranslatorCache();
 
-  friend struct DefaultSingletonTraits<ShaderTranslatorCache>;
-
   // Parameters passed into ShaderTranslator::Init
   struct ShaderTranslatorInitParams {
     ShShaderType shader_type;
     ShShaderSpec shader_spec;
     ShBuiltInResources resources;
     ShaderTranslatorInterface::GlslImplementationType
         glsl_implementation_type;
     ShCompileOptions driver_bug_workarounds;
 
     ShaderTranslatorInitParams(
@@ skipping 26 matching lines @@
   typedef std::map<ShaderTranslatorInitParams, ShaderTranslator* > Cache;
   Cache cache_;
 
   DISALLOW_COPY_AND_ASSIGN(ShaderTranslatorCache);
 };
 
 }  // namespace gles2
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_SERVICE_SHADER_TRANSLATOR_CACHE_H_