Run clang-modernize -use-nullptr over src/extensions/.

extensions/browser/content_hash_fetcher.cc

Index: extensions/browser/content_hash_fetcher.cc
diff --git a/extensions/browser/content_hash_fetcher.cc b/extensions/browser/content_hash_fetcher.cc
index aa3475e94e1c448dfbb04a287e6a5eebef154832..571e02b20766469a87122896738cddd44d6f438a 100644
--- a/extensions/browser/content_hash_fetcher.cc
+++ b/extensions/browser/content_hash_fetcher.cc
@@ -254,7 +254,7 @@ void ContentHashFetcherJob::DoneCheckingForVerifiedContents(bool found) {
 static int WriteFileHelper(const base::FilePath& path,
                            scoped_ptr<std::string> content) {
   base::FilePath dir = path.DirName();
-  return (base::CreateDirectoryAndGetError(dir, NULL) &&
+  return (base::CreateDirectoryAndGetError(dir, nullptr) &&
           base::WriteFile(path, content->data(), content->size()));
 }
 
@@ -341,7 +341,7 @@ bool ContentHashFetcherJob::CreateHashes(const base::FilePath& hashes_file) {
   if (IsCancelled())
     return false;
   // Make sure the directory exists.
-  if (!base::CreateDirectoryAndGetError(hashes_file.DirName(), NULL))
+  if (!base::CreateDirectoryAndGetError(hashes_file.DirName(), nullptr))
     return false;
 
   if (!verified_contents_.get()) {