Do not expose is_null API for time values in Blink

third_party/WebKit/Source/wtf/Time.h

 // Copyright 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.
 
 #ifndef WTF_Time_h
 #define WTF_Time_h
 
 #include "base/time/time.h"
 #include "wtf/CurrentTime.h"
 
@@ skipping 11 matching lines @@
 
 using TimeDelta = base::TimeDelta;
 
 namespace internal {
 
 template <class WrappedTimeType>
 class TimeWrapper {
  public:
   TimeWrapper() {}
 
-  bool isNull() const { return m_value.is_null(); }
-
   static TimeWrapper Now() {
     if (WTF::getTimeFunctionForTesting()) {
       double seconds = (WTF::getTimeFunctionForTesting())();
       return TimeWrapper() + TimeDelta::FromSecondsD(seconds);
     }
     return TimeWrapper(WrappedTimeType::Now());
   }
 
   int64_t ToInternalValueForTesting() const {
     return m_value.ToInternalValue();
@@ skipping 52 matching lines @@
 using Time = internal::TimeWrapper<base::Time>;
 using TimeTicks = internal::TimeWrapper<base::TimeTicks>;
 
 }  // namespace WTF
 
 using WTF::Time;
 using WTF::TimeDelta;
 using WTF::TimeTicks;
 
 #endif  // Time_h