Replace NULL with nullptr in all C++ files.

webrtc/modules/video_coding/receiver_unittest.cc

 /*  Copyright (c) 2013 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.
  */
 
 #include <string.h>
@@ skipping 421 matching lines @@
   // build bot to kill the test.
   while (num_frames_return < kNumFrames) {
     int64_t start_time = clock_.TimeInMilliseconds();
     VCMEncodedFrame* frame = receiver_.FrameForDecoding(kMaxWaitTime, false);
     int64_t end_time = clock_.TimeInMilliseconds();
 
     // In any case the FrameForDecoding should not wait longer than
     // max_wait_time.
     // In the case that we did not get a frame, it should have been waiting for
     // exactly max_wait_time. (By the testing samples we constructed above, we
-    // are sure there is no timing error, so the only case it returns with NULL
+    // are sure there is no timing error, so the only case it returns with null
     // is that it runs out of time.)
     if (frame) {
       receiver_.ReleaseFrame(frame);
       ++num_frames_return;
       EXPECT_GE(kMaxWaitTime, end_time - start_time);
     } else {
       EXPECT_EQ(kMaxWaitTime, end_time - start_time);
     }
   }
 }
@@ skipping 46 matching lines @@
                 end_time);
       receiver_.ReleaseFrame(frame);
       ++num_frames_return;
     } else {
       EXPECT_EQ(kMaxWaitTime, end_time - start_time);
     }
   }
 }
 
 }  // namespace webrtc