Fix net_perftests
Fix net_perftests

Without this, I am reliably getting the following crash. It looks like the timer may fire (in the nested MessageLoop run call inside TestCompletionCallback::WaitForResult) before the expected num_callbacks_ gets set.


[ RUN      ] DiskCacheTest.CacheBackendPerformance
[18893:18893:0511/165403:1994535049146:FATAL:disk_cache_test_util.cc(174)] Check failed: false. 
Backtrace:
	base::debug::StackTrace::StackTrace() [0x4ed37e]
	logging::LogMessage::~LogMessage() [0x4fdd12]
	MessageLoopHelper::TimerExpired() [0x4d2589]
	DispatchToMethod<>() [0x4d2b42]
	base::BaseTimer<>::TimerTask::Run() [0x4d29d2]
	(anonymous namespace)::TaskClosureAdapter::Run() [0x4ffac9]
	base::internal::Invoker1<>::DoInvoke() [0x503624]
	base::Callback<>::Run() [0x504799]
	MessageLoop::RunTask() [0x50241c]
	MessageLoop::DeferOrRunPendingTask() [0x502553]
	MessageLoop::DoDelayedWork() [0x502f49]
	base::MessagePumpLibevent::Run() [0x4d9e8b]
	MessageLoop::RunInternal() [0x50222b]
	MessageLoop::RunHandler() [0x5020de]
	MessageLoop::Run() [0x501af9]
	TestCompletionCallback::WaitForResult() [0x4d1681]
	TestCompletionCallback::GetResult() [0x4d16e6]
	(anonymous namespace)::TimeWrite() [0x4136cc]
	DiskCacheTest_CacheBackendPerformance_Test::TestBody() [0x41407b]
	testing::internal::HandleSehExceptionsInMethodIfSupported<>() [0x588785]
	testing::internal::HandleExceptionsInMethodIfSupported<>() [0x585206]
	testing::Test::Run() [0x579066]
	testing::TestInfo::Run() [0x57988a]
	testing::TestCase::Run() [0x579f80]
	testing::internal::UnitTestImpl::RunAllTests() [0x57ed57]


BUG=None
TEST=net_perftests


Review URL: http://codereview.chromium.org/7001028

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@85139 0039d316-1c4b-4281-b951-d872f2087c98

yitian134/chromium,adobe/chromium,ropik/chromium,adobe/chromium,adobe/chromium,yitian134/chromium,adobe/chromium,adobe/chromium,gavinp/chromium,adobe/chromium,ropik/chromium,gavinp/chromium,ropik/chromium,ropik/chromium,ropik/chromium,ropik/chromium,gavinp/chromium,adobe/chromium,yitian134/chromium,yitian134/chromium,gavinp/chromium,adobe/chromium,gavinp/chromium,yitian134/chromium,ropik/chromium,ropik/chromium,yitian134/chromium,adobe/chromium,gavinp/chromium,yitian134/chromium,yitian134/chromium,gavinp/chromium,yitian134/chromium,yitian134/chromium,ropik/chromium,adobe/chromium,gavinp/chromium,gavinp/chromium,adobe/chromium,gavinp/chromium