Record UMA statistics for file_stream operations.

content/browser/download/base_file.cc

Index: content/browser/download/base_file.cc
diff --git a/content/browser/download/base_file.cc b/content/browser/download/base_file.cc
index 7593df8c1c52ed488ab3b19576b6e258ead7a45a..41429b80166fbb777732f755a8e06fba57321d3c 100644
--- a/content/browser/download/base_file.cc
+++ b/content/browser/download/base_file.cc
@@ -36,6 +36,8 @@ BaseFile::BaseFile(const FilePath& full_path,
       detached_(false) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
   memset(sha256_hash_, 0, sizeof(sha256_hash_));
+  if (file_stream_.get())
+    file_stream_->EnableRecording();
 }
 
 BaseFile::~BaseFile() {
@@ -203,6 +205,7 @@ bool BaseFile::Open() {
   // Create a new file stream if it is not provided.
   if (!file_stream_.get()) {
     file_stream_.reset(new net::FileStream);
+    file_stream_->EnableRecording();
     if (file_stream_->Open(full_path_,
                            base::PLATFORM_FILE_OPEN_ALWAYS |
                                base::PLATFORM_FILE_WRITE) != net::OK) {