Convert NULL to nullptr

snapshot/system_snapshot_mac_test.cc

 // Copyright 2014 The Crashpad Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
@@ skipping 32 matching lines @@
         system_snapshot_() {
   }
 
   const internal::SystemSnapshotMac& system_snapshot() const {
     return system_snapshot_;
   }
 
   // testing::Test:
   virtual void SetUp() override {
     ASSERT_TRUE(process_reader_.Initialize(mach_task_self()));
-    ASSERT_EQ(0, gettimeofday(&snapshot_time_, NULL))
+    ASSERT_EQ(0, gettimeofday(&snapshot_time_, nullptr))
         << ErrnoMessage("gettimeofday");
     system_snapshot_.Initialize(&process_reader_, &snapshot_time_);
   }
 
  private:
   ProcessReader process_reader_;
   timeval snapshot_time_;
   internal::SystemSnapshotMac system_snapshot_;
 
   DISALLOW_COPY_AND_ASSIGN(SystemSnapshotMacTest);
@@ skipping 103 matching lines @@
       FAIL() << "dst_delta_seconds " << dst_delta_seconds;
     }
 
     EXPECT_NE(standard_name, daylight_name);
   }
 }
 
 }  // namespace
 }  // namespace test
 }  // namespace crashpad