Replace NULL with nullptr or null in webrtc/base/.

webrtc/base/checks.h

 /*
  *  Copyright 2006 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 145 matching lines @@
 
 // Helper functions for RTC_CHECK_OP macro.
 // The (int, int) specialization works around the issue that the compiler
 // will not instantiate the template version of the function on values of
 // unnamed enum type - see comment below.
 #define DEFINE_RTC_CHECK_OP_IMPL(name)                                       \
   template <class t1, class t2>                                              \
   inline std::string* Check##name##Impl(const t1& v1, const t2& v2,          \
                                         const char* names) {                 \
     if (rtc::safe_cmp::name(v1, v2))                                         \
-      return NULL;                                                           \
+      return nullptr;                                                        \
     else                                                                     \
       return rtc::MakeCheckOpString(v1, v2, names);                          \
   }                                                                          \
   inline std::string* Check##name##Impl(int v1, int v2, const char* names) { \
     if (rtc::safe_cmp::name(v1, v2))                                         \
-      return NULL;                                                           \
+      return nullptr;                                                        \
     else                                                                     \
       return rtc::MakeCheckOpString(v1, v2, names);                          \
   }
 DEFINE_RTC_CHECK_OP_IMPL(Eq)
 DEFINE_RTC_CHECK_OP_IMPL(Ne)
 DEFINE_RTC_CHECK_OP_IMPL(Le)
 DEFINE_RTC_CHECK_OP_IMPL(Lt)
 DEFINE_RTC_CHECK_OP_IMPL(Ge)
 DEFINE_RTC_CHECK_OP_IMPL(Gt)
 #undef DEFINE_RTC_CHECK_OP_IMPL
@@ skipping 97 matching lines @@
 #define RTC_DCHECK_EQ(a, b) RTC_DCHECK((a) == (b))
 #define RTC_DCHECK_NE(a, b) RTC_DCHECK((a) != (b))
 #define RTC_DCHECK_LE(a, b) RTC_DCHECK((a) <= (b))
 #define RTC_DCHECK_LT(a, b) RTC_DCHECK((a) < (b))
 #define RTC_DCHECK_GE(a, b) RTC_DCHECK((a) >= (b))
 #define RTC_DCHECK_GT(a, b) RTC_DCHECK((a) > (b))
 
 #endif  // __cplusplus
 
 #endif  // WEBRTC_BASE_CHECKS_H_