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

BUG=webrtc:7147

Review-Url: https://codereview.webrtc.org/2718663005
Cr-Commit-Position: refs/heads/master@{#16878}
diff --git a/webrtc/base/logging_unittest.cc b/webrtc/base/logging_unittest.cc
index 5035035..3d9fc9e 100644
--- a/webrtc/base/logging_unittest.cc
+++ b/webrtc/base/logging_unittest.cc
@@ -37,7 +37,7 @@
 // Test basic logging operation. We should get the INFO log but not the VERBOSE.
 // We should restore the correct global state at the end.
 TEST(LogTest, SingleStream) {
-  int sev = LogMessage::GetLogToStream(NULL);
+  int sev = LogMessage::GetLogToStream(nullptr);
 
   std::string str;
   LogSinkImpl<StringStream> stream(&str);
@@ -52,14 +52,14 @@
   LogMessage::RemoveLogToStream(&stream);
   EXPECT_EQ(LS_NONE, LogMessage::GetLogToStream(&stream));
 
-  EXPECT_EQ(sev, LogMessage::GetLogToStream(NULL));
+  EXPECT_EQ(sev, LogMessage::GetLogToStream(nullptr));
 }
 
 // Test using multiple log streams. The INFO stream should get the INFO message,
 // the VERBOSE stream should get the INFO and the VERBOSE.
 // We should restore the correct global state at the end.
 TEST(LogTest, MultipleStreams) {
-  int sev = LogMessage::GetLogToStream(NULL);
+  int sev = LogMessage::GetLogToStream(nullptr);
 
   std::string str1, str2;
   LogSinkImpl<StringStream> stream1(&str1), stream2(&str2);
@@ -81,7 +81,7 @@
   EXPECT_EQ(LS_NONE, LogMessage::GetLogToStream(&stream2));
   EXPECT_EQ(LS_NONE, LogMessage::GetLogToStream(&stream1));
 
-  EXPECT_EQ(sev, LogMessage::GetLogToStream(NULL));
+  EXPECT_EQ(sev, LogMessage::GetLogToStream(nullptr));
 }
 
 // Ensure we don't crash when adding/removing streams while threads are going.
@@ -100,7 +100,7 @@
 };
 
 TEST(LogTest, MultipleThreads) {
-  int sev = LogMessage::GetLogToStream(NULL);
+  int sev = LogMessage::GetLogToStream(nullptr);
 
   LogThread thread1, thread2, thread3;
   thread1.Start();
@@ -117,7 +117,7 @@
     LogMessage::RemoveLogToStream(&stream3);
   }
 
-  EXPECT_EQ(sev, LogMessage::GetLogToStream(NULL));
+  EXPECT_EQ(sev, LogMessage::GetLogToStream(nullptr));
 }
 
 
@@ -137,11 +137,11 @@
 
 TEST(LogTest, MAYBE_Perf) {
   Pathname path;
-  EXPECT_TRUE(Filesystem::GetTemporaryFolder(path, true, NULL));
+  EXPECT_TRUE(Filesystem::GetTemporaryFolder(path, true, nullptr));
   path.SetPathname(Filesystem::TempFilename(path, "ut"));
 
   LogSinkImpl<FileStream> stream;
-  EXPECT_TRUE(stream.Open(path.pathname(), "wb", NULL));
+  EXPECT_TRUE(stream.Open(path.pathname(), "wb", nullptr));
   stream.DisableBuffering();
   LogMessage::AddLogToStream(&stream, LS_SENSITIVE);