shill: Replace NULL with nullptr.

BUG=None
TEST=`USE=wimax FEATURES=test emerge-$BOARD shill`

Change-Id: I30ab47ff32dcadad09ae7a2baf4d4123a6ef0d8e
Reviewed-on: https://chromium-review.googlesource.com/220657
Reviewed-by: Ben Chan <benchan@chromium.org>
Tested-by: Ben Chan <benchan@chromium.org>
Commit-Queue: Ben Chan <benchan@chromium.org>
diff --git a/file_reader.cc b/file_reader.cc
index 7440253..6b841ee 100644
--- a/file_reader.cc
+++ b/file_reader.cc
@@ -23,14 +23,14 @@
 
 bool FileReader::Open(const FilePath &file_path) {
   file_.reset(base::OpenFile(file_path, "rb"));
-  return file_.get() != NULL;
+  return file_.get() != nullptr;
 }
 
 bool FileReader::ReadLine(string *line) {
   CHECK(line) << "Invalid argument";
 
   FILE *fp = file_.get();
-  if (fp == NULL)
+  if (!fp)
     return false;
 
   line->clear();