Use the extensions generated by FeatureInfo in the passthrough cmd decoder.

gpu/command_buffer/service/gles2_cmd_decoder_passthrough.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.
 
 // This file contains the GLES2DecoderPassthroughImpl class.
 
 #ifndef GPU_COMMAND_BUFFER_SERVICE_GLES2_CMD_DECODER_PASSTHROUGH_H_
 #define GPU_COMMAND_BUFFER_SERVICE_GLES2_CMD_DECODER_PASSTHROUGH_H_
 
 #include "base/memory/ref_counted.h"
@@ skipping 260 matching lines @@
   }
 
   template <typename T>
   error::Error PatchGetNumericResults(GLenum pname, GLsizei length, T* params);
   error::Error PatchGetFramebufferAttachmentParameter(GLenum target,
                                                       GLenum attachment,
                                                       GLenum pname,
                                                       GLsizei length,
                                                       GLint* params);
 
-  void BuildExtensionsString();
-
   void InsertError(GLenum error, const std::string& message);
   GLenum PopError();
   bool FlushErrors();
 
   bool IsEmulatedQueryTarget(GLenum target) const;
   error::Error ProcessQueries(bool did_finish);
 
   void UpdateTextureBinding(GLenum target, GLuint client_id, GLuint service_id);
 
   int commands_to_process_;
@@ skipping 78 matching lines @@
   // Currently active queries
   struct ActiveQuery {
     GLuint service_id = 0;
     int32_t shm_id = 0;
     uint32_t shm_offset = 0;
   };
   std::unordered_map<GLenum, ActiveQuery> active_queries_;
 
   std::set<GLenum> errors_;
 
-  std::vector<std::string> emulated_extensions_;
-  std::string extension_string_;
-
   // Cache of scratch memory
   std::vector<uint8_t> scratch_memory_;
 
 // Include the prototypes of all the doer functions from a separate header to
 // keep this file clean.
 #include "gpu/command_buffer/service/gles2_cmd_decoder_passthrough_doer_prototypes.h"
 };
 
 }  // namespace gles2
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_SERVICE_GLES2_CMD_DECODER_PASSTHROUGH_H_