Record UMA statistics for file_stream operations.

net/base/net_errors_posix.cc

Index: net/base/net_errors_posix.cc
diff --git a/net/base/net_errors_posix.cc b/net/base/net_errors_posix.cc
index 143912cd5dd51e8bc06075c0f3241589487d09d0..0d8b7de34471895bca3d3ec527e70e4e01130475 100644
--- a/net/base/net_errors_posix.cc
+++ b/net/base/net_errors_posix.cc
@@ -5,12 +5,19 @@
 #include "net/base/net_errors.h"
 
 #include <errno.h>
+#include <stdlib.h>
+#include <string>
+#include <unistd.h>
 
 #include "base/logging.h"
+#include "base/stringprintf.h"
 
 namespace net {
 
 Error MapSystemError(int os_error) {
+  if (os_error != 0)
+    DVLOG(2) << "Error " << os_error;
+
   // There are numerous posix error codes, but these are the ones we thus far
   // find interesting.
   switch (os_error) {
@@ -98,6 +105,8 @@ Error MapSystemError(int os_error) {
       return ERR_ACCESS_DENIED;
     case EUSERS:  // Too many users.
       return ERR_INSUFFICIENT_RESOURCES;
+    case EMFILE:  // Too many open files.
+      return ERR_INSUFFICIENT_RESOURCES;
 
     case 0:
       return OK;