Failing Builds:
https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Linux%20ChromiumOS%20MSan%20Tests/8363
https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Linux%20ChromiumOS%20MSan%20Tests/8364

Example Log Output:

==13001==WARNING: MemorySanitizer: use-of-uninitialized-value
    #0 0x20cca33e in extensions::ProxyEventRouter::OnProxyError(extensions::EventRouterForwarder*, void*, int) ./../../chrome/browser/extensions/api/proxy/proxy_api.cc:48:7
    #1 0x902732e in network::mojom::ProxyErrorClientStubDispatch::Accept(network::mojom::ProxyErrorClient*, mojo::Message*) ./gen/services/network/public/mojom/proxy_config_with_annotation.mojom.cc:795:13
    #2 0x15054ef6 in network::mojom::ProxyErrorClientStub<mojo::RawPtrImplRefTraits<network::mojom::ProxyErrorClient> >::Accept(mojo::Message*) ./gen/services/network/public/mojom/proxy_config_with_annotation.mojom.h:373:12
    #3 0x190e44e9 in mojo::InterfaceEndpointClient::HandleValidatedMessage(mojo::Message*) ./../../mojo/public/cpp/bindings/lib/interface_endpoint_client.cc:423:32
    #4 0x1912e4ca in mojo::FilterChain::Accept(mojo::Message*) ./../../mojo/public/cpp/bindings/lib/filter_chain.cc:40:17
    #5 0x190fb7f2 in mojo::internal::MultiplexRouter::ProcessIncomingMessage(mojo::internal::MultiplexRouter::MessageWrapper*, mojo::internal::MultiplexRouter::ClientCallBehavior, base::SequencedTaskRunner*) ./../../mojo/public/cpp/bindings/lib/multiplex_router.cc:869:42
    #6 0x190f9200 in mojo::internal::MultiplexRouter::Accept(mojo::Message*) ./../../mojo/public/cpp/bindings/lib/multiplex_router.cc:590:38
    #7 0x1912e4ca in mojo::FilterChain::Accept(mojo::Message*) ./../../mojo/public/cpp/bindings/lib/filter_chain.cc:40:17
    #8 0x190dd59f in mojo::Connector::ReadSingleMessage(unsigned int*) ./../../mojo/public/cpp/bindings/lib/connector.cc:457:51
    #9 0x190dfb30 in mojo::Connector::ReadAllAvailableMessages() ./../../mojo/public/cpp/bindings/lib/connector.cc:486:10
    #10 0x1688828b in Run ./../../base/callback.h:129:12
    #11 0x1688828b in mojo::SimpleWatcher::OnHandleReady(int, unsigned int, mojo::HandleSignalsState const&) ./../../mojo/public/cpp/system/simple_watcher.cc:273:0
    #12 0x1494749f in Run ./../../base/callback.h:99:12
    #13 0x1494749f in base::debug::TaskAnnotator::RunTask(char const*, base::PendingTask*) ./../../base/debug/task_annotator.cc:101:0
    #14 0x14623842 in base::MessageLoop::RunTask(base::PendingTask*) ./../../base/message_loop/message_loop.cc:434:46
    #15 0x14624aef in DeferOrRunPendingTask ./../../base/message_loop/message_loop.cc:445:5
    #16 0x14624aef in base::MessageLoop::DoWork() ./../../base/message_loop/message_loop.cc:517:0
    #17 0x1493392c in base::MessagePumpLibevent::Run(base::MessagePump::Delegate*) ./../../base/message_loop/message_pump_libevent.cc:210:31
    #18 0x146e233f in base::RunLoop::Run() ./../../base/run_loop.cc:102:14
    #19 0x1dc3f17 in (anonymous namespace)::NetworkContextConfigurationBrowserTest::TestProxyConfigured(bool) ./../../chrome/browser/net/network_context_configuration_browsertest.cc:404:26
    #20 0x1657625b in content::BrowserTestBase::ProxyRunTestOnMainThreadLoop() ./../../content/public/test/browser_test_base.cc:415:5
    #21 0x14cebd1f in Run ./../../base/callback.h:129:12
    #22 0x14cebd1f in ChromeBrowserMainParts::PreMainMessageLoopRunImpl() ./../../chrome/browser/chrome_browser_main.cc:2013:0
    #23 0x14ce759b in ChromeBrowserMainParts::PreMainMessageLoopRun() ./../../chrome/browser/chrome_browser_main.cc:1397:18
    #24 0x7e1d2b3 in chromeos::ChromeBrowserMainPartsChromeos::PreMainMessageLoopRun() ./../../chrome/browser/chromeos/chrome_browser_main_chromeos.cc:692:32
    #25 0xcd343ca in content::BrowserMainLoop::PreMainMessageLoopRun() ./../../content/browser/browser_main_loop.cc:1013:13
    #26 0xe43ee0c in Run ./../../base/callback.h:129:12
    #27 0xe43ee0c in content::StartupTaskRunner::RunAllTasksNow() ./../../content/browser/startup_task_runner.cc:43:0
    #28 0xcd2be31 in content::BrowserMainLoop::CreateStartupTasks() ./../../content/browser/browser_main_loop.cc:924:25
    #29 0xcd40919 in content::BrowserMainRunnerImpl::Initialize(content::MainFunctionParams const&) ./../../content/browser/browser_main_runner_impl.cc:140:15
    #30 0xcd20825 in content::BrowserMain(content::MainFunctionParams const&) ./../../content/browser/browser_main.cc:43:32
    #31 0x141d7bfa in RunBrowserProcessMain ./../../content/app/content_main_runner_impl.cc:538:10
    #32 0x141d7bfa in content::ContentMainRunnerImpl::Run(bool) ./../../content/app/content_main_runner_impl.cc:903:0
    #33 0x1ebc6850 in service_manager::Main(service_manager::MainParams const&) ./../../services/service_manager/embedder/main.cc:472:29
    #34 0x141cf044 in content::ContentMain(content::ContentMainParams const&) ./../../content/app/content_main.cc:19:10
    #35 0x16574720 in content::BrowserTestBase::SetUp() ./../../content/public/test/browser_test_base.cc:327:3
    #36 0x14b1bcf2 in InProcessBrowserTest::SetUp() ./../../chrome/test/base/in_process_browser_test.cc:257:20
    #37 0x95aed75 in HandleExceptionsInMethodIfSupported<testing::Test, void> ./../../third_party/googletest/src/googletest/src/gtest.cc:0:0
    #38 0x95aed75 in testing::Test::Run() ./../../third_party/googletest/src/googletest/src/gtest.cc:2518:0
    #39 0x95b2da7 in testing::TestInfo::Run() ./../../third_party/googletest/src/googletest/src/gtest.cc:2698:11
    #40 0x95b4899 in testing::TestCase::Run() ./../../third_party/googletest/src/googletest/src/gtest.cc:2816:28
    #41 0x95edad4 in testing::internal::UnitTestImpl::RunAllTests() ./../../third_party/googletest/src/googletest/src/gtest.cc:5182:43
    #42 0x95ec3a7 in HandleExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool> ./../../third_party/googletest/src/googletest/src/gtest.cc:0:0
    #43 0x95ec3a7 in testing::UnitTest::Run() ./../../third_party/googletest/src/googletest/src/gtest.cc:4791:0
    #44 0x14b91a80 in RUN_ALL_TESTS ./../../third_party/googletest/src/googletest/include/gtest/gtest.h:2333:46
    #45 0x14b91a80 in base::TestSuite::Run() ./../../base/test/test_suite.cc:295:0
    #46 0x1456944c in ChromeTestSuiteRunner::RunTestSuite(int, char**) ./../../chrome/test/base/chrome_test_launcher.cc:71:21
    #47 0x16627e80 in content::LaunchTests(content::TestLauncherDelegate*, unsigned long, int, char**) ./../../content/public/test/test_launcher.cc:645:31
    #48 0x1456ab95 in LaunchChromeTests(unsigned long, content::TestLauncherDelegate*, int, char**) ./../../chrome/test/base/chrome_test_launcher.cc:182:10
    #49 0x14569200 in main ./../../chrome/test/base/browser_tests_main_chromeos.cc:21:10
    #50 0x7f10644f4f44 in __libc_start_main /build/eglibc-ripdx6/eglibc-2.19/csu/libc-start.c:287:0
    #51 0xb726e9 in _start ??:0:0
  Uninitialized value was created by a heap allocation
    #0 0xbe6139 in operator new(unsigned long) /b/swarming/w/ir/kitchen-workdir/src/third_party/llvm/compiler-rt/lib/msan/msan_new_delete.cc:46:35
    #1 0x15ad08d9 in make_unique<SystemNetworkContextManager> ./../../buildtools/third_party/libc++/trunk/include/memory:3114:28
    #2 0x15ad08d9 in BrowserProcessImpl::PreCreateThreads(base::CommandLine const&) ./../../chrome/browser/browser_process_impl.cc:1156:0
    #3 0x14ce563f in ChromeBrowserMainParts::PreCreateThreadsImpl() ./../../chrome/browser/chrome_browser_main.cc:1351:21
    #4 0x14ce1e2c in ChromeBrowserMainParts::PreCreateThreads() ./../../chrome/browser/chrome_browser_main.cc:1065:18
    #5 0xcd29af5 in content::BrowserMainLoop::PreCreateThreads() ./../../content/browser/browser_main_loop.cc:817:28
    #6 0xe43ee0c in Run ./../../base/callback.h:129:12
    #7 0xe43ee0c in content::StartupTaskRunner::RunAllTasksNow() ./../../content/browser/startup_task_runner.cc:43:0
    #8 0xcd2be31 in content::BrowserMainLoop::CreateStartupTasks() ./../../content/browser/browser_main_loop.cc:924:25
    #9 0xcd40919 in content::BrowserMainRunnerImpl::Initialize(content::MainFunctionParams const&) ./../../content/browser/browser_main_runner_impl.cc:140:15
    #10 0xcd20825 in content::BrowserMain(content::MainFunctionParams const&) ./../../content/browser/browser_main.cc:43:32
    #11 0x141d7bfa in RunBrowserProcessMain ./../../content/app/content_main_runner_impl.cc:538:10
    #12 0x141d7bfa in content::ContentMainRunnerImpl::Run(bool) ./../../content/app/content_main_runner_impl.cc:903:0
    #13 0x1ebc6850 in service_manager::Main(service_manager::MainParams const&) ./../../services/service_manager/embedder/main.cc:472:29
    #14 0x141cf044 in content::ContentMain(content::ContentMainParams const&) ./../../content/app/content_main.cc:19:10
    #15 0x16574720 in content::BrowserTestBase::SetUp() ./../../content/public/test/browser_test_base.cc:327:3
    #16 0x14b1bcf2 in InProcessBrowserTest::SetUp() ./../../chrome/test/base/in_process_browser_test.cc:257:20
    #17 0x95aed75 in HandleExceptionsInMethodIfSupported<testing::Test, void> ./../../third_party/googletest/src/googletest/src/gtest.cc:0:0
    #18 0x95aed75 in testing::Test::Run() ./../../third_party/googletest/src/googletest/src/gtest.cc:2518:0
    #19 0x95b2da7 in testing::TestInfo::Run() ./../../third_party/googletest/src/googletest/src/gtest.cc:2698:11
    #20 0x95b4899 in testing::TestCase::Run() ./../../third_party/googletest/src/googletest/src/gtest.cc:2816:28
    #21 0x95edad4 in testing::internal::UnitTestImpl::RunAllTests() ./../../third_party/googletest/src/googletest/src/gtest.cc:5182:43
    #22 0x95ec3a7 in HandleExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool> ./../../third_party/googletest/src/googletest/src/gtest.cc:0:0
    #23 0x95ec3a7 in testing::UnitTest::Run() ./../../third_party/googletest/src/googletest/src/gtest.cc:4791:0
    #24 0x14b91a80 in RUN_ALL_TESTS ./../../third_party/googletest/src/googletest/include/gtest/gtest.h:2333:46
    #25 0x14b91a80 in base::TestSuite::Run() ./../../base/test/test_suite.cc:295:0

Suspecting r587812, will revert.

Reverted r587812 as r587966 and assigning to CL author. eroman@, please investigate.

 Issue 879508  has been merged into this issue.

 Issue 879506  has been merged into this issue.

 Issue 879505  has been merged into this issue.

 Issue 879501  has been merged into this issue.

 Issue 879500  has been merged into this issue.

 Issue 879498  has been merged into this issue.

 Issue 879497  has been merged into this issue.

 Issue 879496  has been merged into this issue.

Thanks for the revert!
... sorry for the damage

Marking as fixed, since this was fixed by the revert in https://chromium.googlesource.com/chromium/src/+/b8ae9cb3ceebc17db40280a83c5599a2a27bc739 - and I confirmed that was the problem.

Note, I will be re-landing a fixed version of the offending CL, and referencing this bug from it for completeness.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/b9fb9f49403a9a47597db318cd3646284f71b9d2

commit b9fb9f49403a9a47597db318cd3646284f71b9d2
Author: Eric Roman <eroman@chromium.org>
Date: Sat Sep 01 03:37:46 2018

Make chrome.proxy.onProxyError extension API work under the Network Service.

This adds an optional "ProxyErrorClient" client to the NetworkContext which
receives notifications of errors in the PAC script, as well as notifications
of failed URL loads that may have been proxy related.

(Reland of d576f34af2134e4205788845247d5d52063fee1f).

Bug:  876568 , 851609 , 879491 
Cq-Include-Trybots: luci.chromium.try:linux_mojo
Change-Id: I08987d658879913d94c9b13b6fdc1de2a32a6d54
Reviewed-on: https://chromium-review.googlesource.com/1200076
Commit-Queue: Eric Roman <eroman@chromium.org>
Reviewed-by: Will Harris <wfh@chromium.org>
Reviewed-by: Matt Menke <mmenke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#588259}
[modify] https://crrev.com/b9fb9f49403a9a47597db318cd3646284f71b9d2/chrome/browser/net/chrome_extensions_network_delegate.cc
[modify] https://crrev.com/b9fb9f49403a9a47597db318cd3646284f71b9d2/chrome/browser/net/chrome_extensions_network_delegate.h
[modify] https://crrev.com/b9fb9f49403a9a47597db318cd3646284f71b9d2/chrome/browser/net/chrome_network_delegate.cc
[modify] https://crrev.com/b9fb9f49403a9a47597db318cd3646284f71b9d2/chrome/browser/net/chrome_network_delegate.h
[modify] https://crrev.com/b9fb9f49403a9a47597db318cd3646284f71b9d2/chrome/browser/net/proxy_config_monitor.cc
[modify] https://crrev.com/b9fb9f49403a9a47597db318cd3646284f71b9d2/chrome/browser/net/proxy_config_monitor.h
[modify] https://crrev.com/b9fb9f49403a9a47597db318cd3646284f71b9d2/net/base/layered_network_delegate.cc
[modify] https://crrev.com/b9fb9f49403a9a47597db318cd3646284f71b9d2/net/base/layered_network_delegate.h
[modify] https://crrev.com/b9fb9f49403a9a47597db318cd3646284f71b9d2/net/base/layered_network_delegate_unittest.cc
[modify] https://crrev.com/b9fb9f49403a9a47597db318cd3646284f71b9d2/services/network/network_context.cc
[modify] https://crrev.com/b9fb9f49403a9a47597db318cd3646284f71b9d2/services/network/network_context_unittest.cc
[modify] https://crrev.com/b9fb9f49403a9a47597db318cd3646284f71b9d2/services/network/public/mojom/network_context.mojom
[modify] https://crrev.com/b9fb9f49403a9a47597db318cd3646284f71b9d2/services/network/public/mojom/proxy_config_with_annotation.mojom
[modify] https://crrev.com/b9fb9f49403a9a47597db318cd3646284f71b9d2/testing/buildbot/filters/mojo.fyi.network_browser_tests.filter