Do not DCHECK on SimpleCache deletion-while-closing.

net/disk_cache/simple/simple_index_file.cc

 // Copyright (c) 2013 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/disk_cache/simple/simple_index_file.h"
 
 #include <vector>
 
 #include "base/files/file.h"
 #include "base/files/file_util.h"
@@ skipping 53 matching lines @@
 void UmaRecordIndexInitMethod(IndexInitMethod method,
                               net::CacheType cache_type) {
   SIMPLE_CACHE_UMA(ENUMERATION,
                    "IndexInitializeMethod", cache_type,
                    method, INITIALIZE_METHOD_MAX);
 }
 
 bool WritePickleFile(Pickle* pickle, const base::FilePath& file_name) {
   File file(
       file_name,
-      File::FLAG_CREATE_ALWAYS | File::FLAG_WRITE | File::FLAG_SHARE_DELETE);
+      File::FLAG_CREATE | File::FLAG_WRITE | File::FLAG_SHARE_DELETE);

[gavinp, 2014/10/30 18:59:20]

This change is good to do while we are here: if multiple serializations of the
same index are overlapping, this causes the second one to abort. This may
actually enhance the entry not found problem you describe in the underlying
issue; esp on Linux, so expect some changes here.

   if (!file.IsValid())
     return false;
 
   int bytes_written =
       file.Write(0, static_cast<const char*>(pickle->data()), pickle->size());
   if (bytes_written != implicit_cast<int>(pickle->size())) {
     simple_util::SimpleCacheDeleteFile(file_name);
     return false;
   }
   return true;
@@ skipping 130 matching lines @@
       LOG(ERROR) << "Could not create a directory to hold the index file";
       return;
     }
     if (!WritePickleFile(pickle.get(), temp_index_filename)) {
       LOG(ERROR) << "Failed to write the temporary index file";
       return;
     }
   }
 
   // Atomically rename the temporary index file to become the real one.
-  bool result = base::ReplaceFile(temp_index_filename, index_filename, NULL);
-  DCHECK(result);
+  if (!base::ReplaceFile(temp_index_filename, index_filename, NULL))
+    return;
 

[jkarlin, 2014/10/30 19:19:24]

Would be better to replace DCHECK(result) with DCHECK(result || shutting_down)
so that other writes are still checked.

[gavinp, 2014/10/31 13:55:54]

That data isn't easily available here; it would require some plumbing through.
I've added a TODO and a discussion of the reasoning.

   if (app_on_background) {
     SIMPLE_CACHE_UMA(TIMES,
                      "IndexWriteToDiskTime.Background", cache_type,
                      (base::TimeTicks::Now() - start_time));
   } else {
     SIMPLE_CACHE_UMA(TIMES,
                      "IndexWriteToDiskTime.Foreground", cache_type,
                      (base::TimeTicks::Now() - start_time));
   }
 }
@@ skipping 229 matching lines @@
 bool SimpleIndexFile::LegacyIsIndexFileStale(
     base::Time cache_last_modified,
     const base::FilePath& index_file_path) {
   base::Time index_mtime;
   if (!simple_util::GetMTime(index_file_path, &index_mtime))
     return true;
   return index_mtime < cache_last_modified;
 }
 
 }  // namespace disk_cache