just use c++ static_assert everywhere

Source/wtf/Assertions.h

 /*
  * Copyright (C) 2003, 2006, 2007 Apple Inc.  All rights reserved.
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 274 matching lines @@
 #define ASSERT_ARG(argName, assertion) do \
     if (!(assertion)) { \
         WTFReportArgumentAssertionFailure(__FILE__, __LINE__, WTF_PRETTY_FUNCTION, #argName, #assertion); \
         CRASH(); \
     } \
 while (0)
 
 #endif
 
 /* COMPILE_ASSERT */
-#ifndef COMPILE_ASSERT
-#if COMPILER_SUPPORTS(C_STATIC_ASSERT)
-/* Unlike static_assert below, this also works in plain C code. */
-#define COMPILE_ASSERT(exp, name) _Static_assert((exp), #name)
-#elif COMPILER_SUPPORTS(CXX_STATIC_ASSERT)
-#define COMPILE_ASSERT(exp, name) static_assert((exp), #name)
-#else
-#define COMPILE_ASSERT(exp, name) typedef int dummy##name [(exp) ? 1 : -1]
-#endif
+#ifndef COMPILE_ASSERT // also defined in base/macros.h
+#define COMPILE_ASSERT(exp, msg) static_assert((exp), #msg)
 #endif
 
 /* FATAL */
 
 #if FATAL_DISABLED
 #define FATAL(...) ((void)0)
 #else
 #define FATAL(...) do { \
     WTFReportFatalError(__FILE__, __LINE__, WTF_PRETTY_FUNCTION, __VA_ARGS__); \
     CRASH(); \
@@ skipping 91 matching lines @@
 } \
 inline const thisType& to##thisType(const argumentType& argumentName) \
 { \
     ASSERT_WITH_SECURITY_IMPLICATION(referencePredicate); \
     return static_cast<const thisType&>(argumentName); \
 } \
 void to##thisType(const thisType*); \
 void to##thisType(const thisType&)
 
 #endif /* WTF_Assertions_h */