Do not DCHECK on SimpleCache deletion-while-closing.

net/disk_cache/backend_unittest.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 "base/basictypes.h"
 #include "base/files/file_util.h"
 #include "base/metrics/field_trial.h"
 #include "base/port.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
@@ skipping 3463 matching lines @@
 
   scoped_ptr<TestIterator> iter = CreateIterator();
   disk_cache::Entry* entry = NULL;
   ASSERT_EQ(net::OK, iter->OpenNextEntry(&entry));
   EXPECT_TRUE(entry);
   disk_cache::ScopedEntryPtr entry_closer(entry);
 
   cache_.reset();
   // This test passes if we don't leak memory.
 }
+
+// Tests that a SimpleCache doesn't crash when files are deleted very quickly
+// after closing.
+// NOTE: IF THIS TEST IS FLAKY THEN IT IS FAILING.

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

Append the bug that this CL fixes to the test comment.

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

Does this flake at least say 20% of the time?  It needs to flake fairly  often
to be noticed.  How hard would it be to make this test work 100% of the time?

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

I get a 100% failure rate on 100 iterations on my Mac, and that runs in 380ms.
I'm calling that acceptable for now. I'm a bit concerned about windows, so I'll
watch try bots.

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

Done.

+TEST_F(DiskCacheBackendTest, SimpleCacheDeleteQuickly) {
+  SetSimpleCacheMode();
+  InitCache();
+  cache_.reset();
+  EXPECT_TRUE(CleanupCacheDir());
+}