Replace NULL with nullptr in all C++ files.

webrtc/system_wrappers/source/aligned_malloc_unittest.cc

Index: webrtc/system_wrappers/source/aligned_malloc_unittest.cc
diff --git a/webrtc/system_wrappers/source/aligned_malloc_unittest.cc b/webrtc/system_wrappers/source/aligned_malloc_unittest.cc
index fbd5d6e1f65f9b288cea4923a409859a123eca31..9c6eded918dd6f45df648bdcffa391c928195eef 100644
--- a/webrtc/system_wrappers/source/aligned_malloc_unittest.cc
+++ b/webrtc/system_wrappers/source/aligned_malloc_unittest.cc
@@ -27,7 +27,7 @@ namespace webrtc {
 bool CorrectUsage(size_t size, size_t alignment) {
   std::unique_ptr<char, AlignedFreeDeleter> scoped(
       static_cast<char*>(AlignedMalloc(size, alignment)));
-  if (scoped.get() == NULL) {
+  if (scoped.get() == nullptr) {
     return false;
   }
   const uintptr_t scoped_address = reinterpret_cast<uintptr_t> (scoped.get());
@@ -40,7 +40,7 @@ TEST(AlignedMalloc, GetRightAlign) {
   const size_t left_misalignment = 1;
   std::unique_ptr<char, AlignedFreeDeleter> scoped(
       static_cast<char*>(AlignedMalloc(size, alignment)));
-  EXPECT_TRUE(scoped.get() != NULL);
+  EXPECT_TRUE(scoped.get() != nullptr);
   const uintptr_t aligned_address = reinterpret_cast<uintptr_t> (scoped.get());
   const uintptr_t misaligned_address = aligned_address - left_misalignment;
   const char* misaligned_ptr = reinterpret_cast<const char*>(