Guard local time posix functions from NaN value of invalid dates.

src/platform.h

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 125 matching lines @@
   // Get a tick counter normalized to one tick per microsecond.
   // Used for calculating time intervals.
   static int64_t Ticks();
 
   // Returns current time as the number of milliseconds since
   // 00:00:00 UTC, January 1, 1970.
   static double TimeCurrentMillis();
 
   // Returns a string identifying the current time zone. The
   // timestamp is used for determining if DST is in effect.
-  static char* LocalTimezone(double time);
+  static const char* LocalTimezone(double time);
 
   // Returns the local time offset in milliseconds east of UTC without
   // taking daylight savings time into account.
   static double LocalTimeOffset();
 
   // Returns the daylight savings offset for the given time.
   static double DaylightSavingsOffset(double time);
 
   static FILE* FOpen(const char* path, const char* mode);
 
@@ skipping 378 matching lines @@
   bool active_;
   PlatformData* data_;  // Platform specific data.
   DISALLOW_IMPLICIT_CONSTRUCTORS(Sampler);
 };
 
 #endif  // ENABLE_LOGGING_AND_PROFILING
 
 } }  // namespace v8::internal
 
 #endif  // V8_PLATFORM_H_