Record UMA statistics for file_stream operations.

net/base/file_stream.h

Index: net/base/file_stream.h
diff --git a/net/base/file_stream.h b/net/base/file_stream.h
index da42afb944603336fd170ae90016f2cd95633b62..4ce178c4c2f299a567802965c4ef434dab443f1f 100644
--- a/net/base/file_stream.h
+++ b/net/base/file_stream.h
@@ -132,6 +132,9 @@ class NET_EXPORT FileStream {
   // This method should not be called if the stream was opened READ_ONLY.
   int Flush();
 
+  // Turns on UMA error statistics gathering.
+  void EnableErrorStatistics();
+
  private:
   class AsyncContext;
   friend class AsyncContext;
@@ -143,6 +146,7 @@ class NET_EXPORT FileStream {
   base::PlatformFile file_;
   int open_flags_;
   bool auto_closed_;
+  bool record_uma_;
 
   DISALLOW_COPY_AND_ASSIGN(FileStream);
 };