Fixed compile error for unit-tests on linux. We do not include any glew file ...

gpu/command_buffer/service/gl_utils.h

 // Copyright (c) 2009 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 includes all the necessary GL headers and implements some useful
 // utilities.
 
 #ifndef GPU_COMMAND_BUFFER_SERVICE_GL_UTILS_H_
 #define GPU_COMMAND_BUFFER_SERVICE_GL_UTILS_H_
 
+#include <build/build_config.h>
+
 #if defined(UNIT_TEST)
 #include "gpu/command_buffer/service/gl_mock.h"
 #else
 #include <GL/glew.h>
 #if defined(OS_WIN)
 #include <GL/wglew.h>
-#endif
-#include <build/build_config.h>
-#endif
+#elif defined(OS_LINUX)
+#include <GL/glxew.h>
+#endif  // OS_WIN
+#endif  // UNIT_TEST
 
 #define GL_GLEXT_PROTOTYPES 1
 
 // Define this for extra GL error debugging (slower).
 // #define GL_ERROR_DEBUGGING
 #ifdef GL_ERROR_DEBUGGING
 #define CHECK_GL_ERROR() do {                                           \
     GLenum gl_error = glGetError();                                     \
     LOG_IF(ERROR, gl_error != GL_NO_ERROR) << "GL Error :" << gl_error; \
   } while (0)
 #else  // GL_ERROR_DEBUGGING
 #define CHECK_GL_ERROR() void(0)
 #endif  // GL_ERROR_DEBUGGING
 
 #endif  // GPU_COMMAND_BUFFER_SERVICE_GL_UTILS_H_