Ignore yet another report on the filesystem guts

The report looks like this:
WARNING: Possible data race during read of size 1 at 1D0D0AEC: {{{
   T0 (L{L5032}):
    #0  _alloc_osfhnd f:/dd/vctools/crt_bld/self_x86/crt/src/osfinfo.c:85
    #1  _open_osfhandle f:/dd/vctools/crt_bld/self_x86/crt/src/osfinfo.c:381
    #2  testing::internal::WindowsDeathTest::AssumeRole testing/gtest/src/gtest-death-test.cc:708
    #3  net::`anonymous namespace'::PrioritizedDispatcherTest_CancelMissing_Test::TestBody net/base/prioritized_dispatcher_unittest.cc:546
    #4  net::`anonymous namespace'::PrioritizedDispatcherTest_CancelMissing_Test::TestBody net/base/prioritized_dispatcher_unittest.cc:544
    #5  testing::internal::HandleExceptionsInMethodIfSupported testing/gtest/src/gtest.cc:2045
  Concurrent write(s) happened at (OR AFTER) these points:
   T21 (L{L4960, L5035}):
    #0  _close_nolock f:/dd/vctools/crt_bld/self_x86/crt/src/close.c:100
    #1  _close f:/dd/vctools/crt_bld/self_x86/crt/src/close.c:53
    #2  _fclose_nolock f:/dd/vctools/crt_bld/self_x86/crt/src/fclose.c:106
    #3  fclose f:/dd/vctools/crt_bld/self_x86/crt/src/fclose.c:56
    #4  base::CloseFile base/file_util.cc:200
    #5  base::ReadFileToString base/file_util.cc:143
    #6  base::ReadFileToString base/file_util.cc:130
    #7  base::ReadFileToString base/file_util.cc:129
    #8  net::ParseHostsFile net/dns/dns_hosts.cc:161
    #9  net::ParseHostsFile net/dns/dns_hosts.cc:153

BUG=146724
TBR=bruening
NOTRY=true

Review URL: https://codereview.chromium.org/119093011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242724 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242724