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

webrtc/base/checks.cc

 /*
  *  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 49 matching lines @@
 // to get usable symbols on Linux. This is copied from V8. Chromium has a more
 // advanced stace trace system; also more difficult to copy.
 void DumpBacktrace() {
 #if defined(__GLIBCXX__) && !defined(__UCLIBC__)
   void* trace[100];
   int size = backtrace(trace, sizeof(trace) / sizeof(*trace));
   char** symbols = backtrace_symbols(trace, size);
   PrintError("\n==== C stack trace ===============================\n\n");
   if (size == 0) {
     PrintError("(empty)\n");
-  } else if (symbols == NULL) {
+  } else if (symbols == nullptr) {
     PrintError("(no symbols)\n");
   } else {
     for (int i = 1; i < size; ++i) {
       char mangled[201];
       if (sscanf(symbols[i], "%*[^(]%*[(]%200[^)+]", mangled) == 1) {  // NOLINT
         PrintError("%2d: ", i);
         int status;
         size_t length;
-        char* demangled = abi::__cxa_demangle(mangled, NULL, &length, &status);
-        PrintError("%s\n", demangled != NULL ? demangled : mangled);
+        char* demangled =
+            abi::__cxa_demangle(mangled, nullptr, &length, &status);
+        PrintError("%s\n", demangled != nullptr ? demangled : mangled);
         free(demangled);
       } else {
         // If parsing failed, at least print the unparsed symbol.
         PrintError("%s\n", symbols[i]);
       }
     }
   }
   free(symbols);
 #endif
 }
@@ skipping 40 matching lines @@
 template std::string* MakeCheckOpString<std::string, std::string>(
     const std::string&, const std::string&, const char* name);
 #endif
 
 }  // namespace rtc
 
 // Function to call from the C version of the RTC_CHECK and RTC_DCHECK macros.
 NO_RETURN void rtc_FatalMessage(const char* file, int line, const char* msg) {
   rtc::FatalMessage(file, line).stream() << msg;
 }