URLFetcher won't call delegate until file is closed.

net/base/file_stream_metrics.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/base/file_stream_metrics.h"
 
 #include "base/basictypes.h"
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
 
 namespace net {
 
 namespace {
 
 const char* FileErrorSourceStrings[] = {
   "OPEN",
   "WRITE",
   "READ",
   "SEEK",
   "FLUSH",
   "SET_EOF",
-  "GET_SIZE"
+  "GET_SIZE",
+  "CLOSE"
 };
 
 COMPILE_ASSERT(ARRAYSIZE_UNSAFE(FileErrorSourceStrings) ==
                    FILE_ERROR_SOURCE_COUNT,
                file_error_source_enum_has_changed);
 
 void RecordFileErrorTypeCount(FileErrorSource source) {
   UMA_HISTOGRAM_ENUMERATION(
       "Net.FileErrorType_Counts", source, FILE_ERROR_SOURCE_COUNT);
 }
@@ skipping 48 matching lines @@
       UMA_HISTOGRAM_ENUMERATION("Net.FileErrorRange_SetEof", bucket,
                                 max_bucket);
       break;
 
     case FILE_ERROR_SOURCE_GET_SIZE:
       UMA_HISTOGRAM_ENUMERATION("Net.FileError_GetSize", error, max_error);
       UMA_HISTOGRAM_ENUMERATION("Net.FileErrorRange_GetSize", bucket,
                                 max_bucket);
       break;
 
+    case FILE_ERROR_SOURCE_CLOSE:
+      UMA_HISTOGRAM_ENUMERATION("Net.FileError_Close", error, max_error);
+      UMA_HISTOGRAM_ENUMERATION("Net.FileErrorRange_Close", bucket,
+                                max_bucket);
+      break;
+
     default:
       break;
   }
 }
 
 const char* GetFileErrorSourceName(FileErrorSource source) {
   DCHECK_NE(FILE_ERROR_SOURCE_COUNT, source);
   return FileErrorSourceStrings[source];
 }
 
 }  // namespace net