Replace NULL with nullptr in all C++ files.

webrtc/modules/audio_coding/neteq/neteq_unittest.cc

Index: webrtc/modules/audio_coding/neteq/neteq_unittest.cc
diff --git a/webrtc/modules/audio_coding/neteq/neteq_unittest.cc b/webrtc/modules/audio_coding/neteq/neteq_unittest.cc
index b77b734e8a9783cbe59e82d6417801aaa7d29243..973742b46697791ed7a53f0a6d958e87dab6db6c 100644
--- a/webrtc/modules/audio_coding/neteq/neteq_unittest.cc
+++ b/webrtc/modules/audio_coding/neteq/neteq_unittest.cc
@@ -172,7 +172,7 @@ ResultSink::ResultSink(const std::string &output_file)
       digest_(new rtc::Sha1Digest()) {
   if (!output_file.empty()) {
     output_fp_ = fopen(output_file.c_str(), "wb");
-    EXPECT_TRUE(output_fp_ != NULL);
+    EXPECT_TRUE(output_fp_ != nullptr);
   }
 }
 
@@ -288,7 +288,7 @@ const size_t NetEqDecodingTest::kBlockSize32kHz;
 const int NetEqDecodingTest::kInitSampleRateHz;
 
 NetEqDecodingTest::NetEqDecodingTest()
-    : neteq_(NULL),
+    : neteq_(nullptr),
       config_(),
       sim_clock_(0),
       output_sample_rate_(kInitSampleRateHz),