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

webrtc/base/optionsfile_unittest.cc

 /*
  *  Copyright 2008 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 29 matching lines @@
 // Fails on Android: https://bugs.chromium.org/p/webrtc/issues/detail?id=4364.
 #define MAYBE_OptionsFileTest DISABLED_OptionsFileTest
 #else
 #define MAYBE_OptionsFileTest OptionsFileTest
 #endif
 
 class MAYBE_OptionsFileTest : public testing::Test {
  public:
   MAYBE_OptionsFileTest() {
     Pathname dir;
-    RTC_CHECK(Filesystem::GetTemporaryFolder(dir, true, NULL));
+    RTC_CHECK(Filesystem::GetTemporaryFolder(dir, true, nullptr));
     test_file_ = Filesystem::TempFilename(dir, ".testfile");
     OpenStore();
   }
 
   ~MAYBE_OptionsFileTest() override {
     remove(test_file_.c_str());
   }
 
  protected:
   void OpenStore() {
@@ skipping 112 matching lines @@
   EXPECT_TRUE(store_->GetStringValue(kEmptyString, &out));
   EXPECT_EQ(kTestString2, out);
   EXPECT_TRUE(store_->SetStringValue(kTestOptionB, kEmptyString));
   EXPECT_TRUE(store_->Save());
   EXPECT_TRUE(store_->Load());
   EXPECT_TRUE(store_->GetStringValue(kTestOptionB, &out));
   EXPECT_EQ(kEmptyString, out);
 }
 
 }  // namespace rtc