[libutils]  Modernize codebase by replacing NULL with nullptr

Fixes -Wzero-as-null-pointer-constant warning.

Test: m
Bug: 68236239
Change-Id: I5e89ec8c42151875439d2656475a8739ab9cb7dc
diff --git a/libutils/tests/Looper_test.cpp b/libutils/tests/Looper_test.cpp
index 8ebcfaf..2282ced 100644
--- a/libutils/tests/Looper_test.cpp
+++ b/libutils/tests/Looper_test.cpp
@@ -339,7 +339,7 @@
     Pipe pipe;
 
     pipe.writeSignal();
-    mLooper->addFd(pipe.receiveFd, expectedIdent, Looper::EVENT_INPUT, NULL, expectedData);
+    mLooper->addFd(pipe.receiveFd, expectedIdent, Looper::EVENT_INPUT, nullptr, expectedData);
 
     StopWatch stopWatch("pollOnce");
     int fd;
@@ -364,7 +364,7 @@
 
 TEST_F(LooperTest, AddFd_WhenCallbackAdded_ReturnsOne) {
     Pipe pipe;
-    int result = mLooper->addFd(pipe.receiveFd, 0, Looper::EVENT_INPUT, NULL, NULL);
+    int result = mLooper->addFd(pipe.receiveFd, 0, Looper::EVENT_INPUT, nullptr, nullptr);
 
     EXPECT_EQ(1, result)
             << "addFd should return 1 because FD was added";
@@ -372,7 +372,7 @@
 
 TEST_F(LooperTest, AddFd_WhenIdentIsNegativeAndCallbackIsNull_ReturnsError) {
     Pipe pipe;
-    int result = mLooper->addFd(pipe.receiveFd, -1, Looper::EVENT_INPUT, NULL, NULL);
+    int result = mLooper->addFd(pipe.receiveFd, -1, Looper::EVENT_INPUT, nullptr, nullptr);
 
     EXPECT_EQ(-1, result)
             << "addFd should return -1 because arguments were invalid";
@@ -381,7 +381,7 @@
 TEST_F(LooperTest, AddFd_WhenNoCallbackAndAllowNonCallbacksIsFalse_ReturnsError) {
     Pipe pipe;
     sp<Looper> looper = new Looper(false /*allowNonCallbacks*/);
-    int result = looper->addFd(pipe.receiveFd, 0, 0, NULL, NULL);
+    int result = looper->addFd(pipe.receiveFd, 0, 0, nullptr, nullptr);
 
     EXPECT_EQ(-1, result)
             << "addFd should return -1 because arguments were invalid";