Revert "third_party/protobuf: Update to HEAD (83d681ee2c)"

third_party/protobuf/src/google/protobuf/stubs/mathutil.h

 // Protocol Buffers - Google's data interchange format
 // Copyright 2008 Google Inc.  All rights reserved.
 // https://developers.google.com/protocol-buffers/
 //
 // 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.
@@ skipping 23 matching lines @@
 #include <math.h>
 
 #include <google/protobuf/stubs/common.h>
 #include <google/protobuf/stubs/logging.h>
 #include <google/protobuf/stubs/mathlimits.h>
 
 namespace google {
 namespace protobuf {
 namespace internal {
 template<typename T>
+bool IsNan(T value) {
+  return false;
+}
+template<>
+inline bool IsNan(float value) {
+#ifdef _MSC_VER
+  return _isnan(value);
+#else
+  return isnan(value);
+#endif
+}
+template<>
+inline bool IsNan(double value) {
+#ifdef _MSC_VER
+  return _isnan(value);
+#else
+  return isnan(value);
+#endif
+}
+
+template<typename T>
 bool AlmostEquals(T a, T b) {
   return a == b;
 }
 template<>
 inline bool AlmostEquals(float a, float b) {
   return fabs(a - b) < 32 * FLT_EPSILON;
 }
 
 template<>
 inline bool AlmostEquals(double a, double b) {
   return fabs(a - b) < 32 * DBL_EPSILON;
 }
 }  // namespace internal
 
 class MathUtil {
  public:
   template<typename T>
   static T Sign(T value) {
-    if (value == T(0) || MathLimits<T>::IsNaN(value)) {
+    if (value == T(0) || ::google::protobuf::internal::IsNan<T>(value)) {
       return value;
     }
     return value > T(0) ? 1 : -1;
   }
 
   template<typename T>
   static bool AlmostEquals(T a, T b) {
     return ::google::protobuf::internal::AlmostEquals(a, b);
   }
 
@@ skipping 59 matching lines @@
     }
     T relative_margin = static_cast<T>(fraction * Max(Abs(x), Abs(y)));
     return AbsDiff(x, y) <= Max(margin, relative_margin);
   }
 }
 
 }  // namespace protobuf
 }  // namespace google
 
 #endif  // GOOGLE_PROTOBUF_STUBS_MATHUTIL_H_