On my gubuntu desktop, running the ExtensionsSyncPerfTest.P0 case times out 100% of the time. See stack-trace below when the task is terminated, it successfully exits the test case, but hangs somewhere in the browser tests's cleanup (which bizarrely all lives in SetUp()). Interesting to note, I believe this case currently passes on the trybots.

Changing the kNumExtensions constant to something lower (like 10) than 150 makes it work again. Alternatively, removing the chunk of logic to remove the extensions will cause it to exit quickly. We need to figure out two things:

1. Is this case actually testing the all of the sync related activities that are supposed to happen as a result of removing these extensions? Or is it exiting prematurely?
2. What is causing the bad performance, is extensions logic just this slow? What exactly does removing an extension entail? Does it make sense that our process blocks here? Does it need to be this slow? Has extensions regressed?

#0 0x7f539eb21cde base::debug::StackTrace::StackTrace()
#1 0x000005448957 content::(anonymous namespace)::DumpStackTraceSignalHandler()
#2 0x7f5388385cb0 <unknown>
#3 0x7f539f366659 pthread_join
#4 0x7f539ecea4f2 base::PlatformThread::Join()
#5 0x7f539ed01cdb base::Thread::Stop()
#6 0x7f5398ac6f5d content::BrowserProcessSubThread::~BrowserProcessSubThread()
#7 0x7f5398ac6fa9 Still waiting for the following processes to finish:
	out/Default/sync_performance_tests --allow-file-access --gtest_also_run_disabled_tests --gtest_filter=ExtensionsSyncPerfTest.P0 --single_process --user-data-dir=/tmp/.org.chromium.Chromium.x8UDu1/dmlAVRK
content::BrowserProcessSubThread::~BrowserProcessSubThread()
#8 0x7f539809533f std::default_delete<>::operator()()
#9 0x7f5398ab081c std::unique_ptr<>::reset()
#10 0x7f5398aad688 content::(anonymous namespace)::ResetThread_FILE()
#11 0x7f5398aac732 content::BrowserMainLoop::ShutdownThreadsAndCleanUp()
#12 0x7f5398ab6b53 content::BrowserMainRunnerImpl::Shutdown()
#13 0x7f5398aa5485 content::BrowserMain()
#14 0x7f539a88b2c6 content::RunNamedProcessTypeMain()
#15 0x7f539a88d752 content::ContentMainRunnerImpl::Run()
#16 0x7f539a88a362 content::ContentMain()
#17 0x000005448376 content::BrowserTestBase::SetUp()
#18 0x000001d9337e InProcessBrowserTest::SetUp()
#19 0x000001d7957b SyncTest::SetUp()
#20 0x000001de3bfa testing::internal::HandleSehExceptionsInMethodIfSupported<>()
#21 0x000001dd465e testing::internal::HandleExceptionsInMethodIfSupported<>()
#22 0x000001dc92d3 testing::Test::Run()
#23 0x000001dc9ac8 testing::TestInfo::Run()
#24 0x000001dca06a testing::TestCase::Run()
#25 0x000001dcf3bc testing::internal::UnitTestImpl::RunAllTests()
#26 0x000001de840a testing::internal::HandleSehExceptionsInMethodIfSupported<>()
#27 0x000001dd5e7e testing::internal::HandleExceptionsInMethodIfSupported<>()
#28 0x000001dcf05f testing::UnitTest::Run()
#29 0x000004b8e691 RUN_ALL_TESTS()
#30 0x000004b8d592 base::TestSuite::Run()
#31 0x000004b8bb3c ChromeTestSuiteRunner::RunTestSuite()
#32 0x000004b8bc39 ChromeTestLauncherDelegate::RunTestSuite()
#33 0x0000054628c2 content::LaunchTests()
#34 0x000004b8bfc9 LaunchChromeTests()
#35 0x0000006093a7 main
#36 0x7f5388370f45 __libc_start_main
#37 0x0000005f2115 <unknown>
[1/1] ExtensionsSyncPerfTest.P0 (TIMED OUT)
1 test timed out:
    ExtensionsSyncPerfTest.P0 (../../chrome/browser/sync/test/integration/performance/extensions_sync_perf_test.cc:79)