John: any idea who owns this builder?

I don't think memory builders have particular owners. Sheriffs are expected to keep them green.

https://chromium-review.googlesource.com/c/chromium/src/+/1188848 seems like it might be responsible. discussing offline.

I'm going to take a look.

Ok so it seems like a lot of tests are exercising the same code path where an uninialized value is used. See log below. If this is true this should be an easy fix.

0 0x4d67633 in ash::ShelfWidget::DelegateView::UpdateOpaqueBackground() ./../../ash/shelf/shelf_widget.cc:196:9
    #1 0x4d66846 in ash::ShelfWidget::DelegateView::DelegateView(ash::ShelfWidget*) ./../../ash/shelf/shelf_widget.cc:134:3
    #2 0x4d68de5 in ash::ShelfWidget::ShelfWidget(aura::Window*, ash::Shelf*) ./../../ash/shelf/shelf_widget.cc:246:26
    #3 0x4cebdfb in ash::Shelf::CreateShelfWidget(aura::Window*) ./../../ash/shelf/shelf.cc:73:27
    #4 0x4c9ae65 in ash::RootWindowController::InitLayoutManagers() ./../../ash/root_window_controller.cc:698:11
    #5 0x4c90ccf in ash::RootWindowController::Init(ash::RootWindowController::RootWindowType) ./../../ash/root_window_controller.cc:662:3
    #6 0x4aca1ea in ash::WindowTreeHostManager::InitHosts() ./../../ash/display/window_tree_host_manager.cc:238:3
    #7 0x4d79e78 in ash::Shell::Init(ui::ContextFactory*, ui::ContextFactoryPrivate*, std::__1::unique_ptr<base::Value, std::__1::default_delete<base::Value> >, std::__1::unique_ptr<ui::ws2::GpuInterfaceProvider, std::__1::default_delete<ui::ws2::GpuInterfaceProvider> >) ./../../ash/shell.cc:1259:30
    #8 0x4d700c9 in ash::Shell::CreateInstance(ash::ShellInitParams) ./../../ash/shell.cc:275:14
    #9 0x9ebc458 in ash::AshTestHelper::CreateShell() ./../../ash/test/ash_test_helper.cc:395:3
    #10 0x9ebb3fa in ash::AshTestHelper::SetUp(bool, bool) ./../../ash/test/ash_test_helper.cc:247:3
    #11 0x9eb2843 in ash::AshTestBase::SetUp() ./../../ash/test/ash_test_base.cc:158:21
    #12 0x756c19 in ash::(anonymous namespace)::PreferredReservedAcceleratorsTest::SetUp() ./../../ash/accelerators/accelerator_controller_unittest.cc:988:18
    #13 0x46ef905 in testing::Test::Run() ./../../third_party/googletest/src/googletest/src/gtest.cc:0:0
    #14 0x46f3447 in testing::TestInfo::Run() ./../../third_party/googletest/src/googletest/src/gtest.cc:2698:11
    #15 0x46f4f39 in testing::TestCase::Run() ./../../third_party/googletest/src/googletest/src/gtest.cc:2816:28
    #16 0x472e1d4 in testing::internal::UnitTestImpl::RunAllTests() ./../../third_party/googletest/src/googletest/src/gtest.cc:5182:43
    #17 0x472caa7 in testing::UnitTest::Run() ./../../third_party/googletest/src/googletest/src/gtest.cc:0:0
    #18 0x57741b0 in RUN_ALL_TESTS ./../../third_party/googletest/src/googletest/include/gtest/gtest.h:2333:46
    #19 0x57741b0 in base::TestSuite::Run() ./../../base/test/test_suite.cc:295:0
    #20 0x577bf0f in Run ./../../base/callback.h:99:12
    #21 0x577bf0f in base::(anonymous namespace)::LaunchUnitTestsInternal(base::OnceCallback<int ()>, unsigned long, int, bool, base::OnceCallback<void ()>) ./../../base/test/launcher/unit_test_launcher.cc:224:0
    #22 0x577b6b7 in base::LaunchUnitTests(int, char**, base::OnceCallback<int ()>) ./../../base/test/launcher/unit_test_launcher.cc:575:10
    #23 0x22063a6 in main ./../../ash/test/ash_unittests.cc:37:10
    #24 0x7f701363bf44 in __libc_start_main /build/eglibc-ripdx6/eglibc-2.19/csu/libc-start.c:287:0
    #25 0x647949 in _start ??:0:0
  Uninitialized value was created by a heap allocation
    #0 0x6bb479 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 0x4cebdb3 in ash::Shelf::CreateShelfWidget(aura::Window*) ./../../ash/shelf/shelf.cc:73:23
    #2 0x4c9ae65 in ash::RootWindowController::InitLayoutManagers() ./../../ash/root_window_controller.cc:698:11
    #3 0x4c90ccf in ash::RootWindowController::Init(ash::RootWindowController::RootWindowType) ./../../ash/root_window_controller.cc:662:3
    #4 0x4aca1ea in ash::WindowTreeHostManager::InitHosts() ./../../ash/display/window_tree_host_manager.cc:238:3
    #5 0x4d79e78 in ash::Shell::Init(ui::ContextFactory*, ui::ContextFactoryPrivate*, std::__1::unique_ptr<base::Value, std::__1::default_delete<base::Value> >, std::__1::unique_ptr<ui::ws2::GpuInterfaceProvider, std::__1::default_delete<ui::ws2::GpuInterfaceProvider> >) ./../../ash/shell.cc:1259:30
    #6 0x4d700c9 in ash::Shell::CreateInstance(ash::ShellInitParams) ./../../ash/shell.cc:275:14
    #7 0x9ebc458 in ash::AshTestHelper::CreateShell() ./../../ash/test/ash_test_helper.cc:395:3
    #8 0x9ebb3fa in ash::AshTestHelper::SetUp(bool, bool) ./../../ash/test/ash_test_helper.cc:247:3
    #9 0x9eb2843 in ash::AshTestBase::SetUp() ./../../ash/test/ash_test_base.cc:158:21
    #10 0x756c19 in ash::(anonymous namespace)::PreferredReservedAcceleratorsTest::SetUp() ./../../ash/accelerators/accelerator_controller_unittest.cc:988:18
    #11 0x46ef905 in testing::Test::Run() ./../../third_party/googletest/src/googletest/src/gtest.cc:0:0
    #12 0x46f3447 in testing::TestInfo::Run() ./../../third_party/googletest/src/googletest/src/gtest.cc:2698:11
    #13 0x46f4f39 in testing::TestCase::Run() ./../../third_party/googletest/src/googletest/src/gtest.cc:2816:28
    #14 0x472e1d4 in testing::internal::UnitTestImpl::RunAllTests() ./../../third_party/googletest/src/googletest/src/gtest.cc:5182:43
    #15 0x472caa7 in testing::UnitTest::Run() ./../../third_party/googletest/src/googletest/src/gtest.cc:0:0
    #16 0x57741b0 in RUN_ALL_TESTS ./../../third_party/googletest/src/googletest/include/gtest/gtest.h:2333:46
    #17 0x57741b0 in base::TestSuite::Run() ./../../base/test/test_suite.cc:295:0
    #18 0x577bf0f in Run ./../../base/callback.h:99:12
    #19 0x577bf0f in base::(anonymous namespace)::LaunchUnitTestsInternal(base::OnceCallback<int ()>, unsigned long, int, bool, base::OnceCallback<void ()>) ./../../base/test/launcher/unit_test_launcher.cc:224:0
    #20 0x577b6b7 in base::LaunchUnitTests(int, char**, base::OnceCallback<int ()>) ./../../base/test/launcher/unit_test_launcher.cc:575:10
    #21 0x22063a6 in main ./../../ash/test/ash_unittests.cc:37:10

==25117==WARNING: MemorySanitizer: use-of-uninitialized-value

(Prepended to that log)

Sent out tentative fix in CL 1195604

Trying to chase down an owner. If you have owner rights over

    ash/shelf/shelf_widget.h
    ash/shelf/shelf_widget.cc

you can help me review this change :-)

    https://chromium-review.googlesource.com/c/chromium/src/+/1195604

$ cat ash/shelf/OWNERS 
msw@chromium.org
skuhne@chromium.org
xiyuan@chromium.org

Thanks Evan! Yeah they're all in MTV and none of them seems available, I was hoping to find someone in another time zone. I guess I'll wait until morning MTV time.

Oops, I reverted the offending CL, failing to find this bug. (Seemed too bad
to leave 10+ test suites failing more than O(1000) tests)

Feel free to reland when your fix is ready.

No worries, you did what you had to :-)

CL 1196426 fixed it. Closing.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a76b6b005860e9cec83f751e6c2ae0daff0a21b5

commit a76b6b005860e9cec83f751e6c2ae0daff0a21b5
Author: Manu Cornet <manucornet@chromium.org>
Date: Thu Aug 30 21:02:23 2018

Reland "CrOS shelf: switch to feature mechanism and enable by default"

Reland without any modifications since the MSAN issue was fixed
separately in CL 1196426

This is a reland of 6442a85088c64c17db646374c94e78cca6f19b99

Original change's description:
> CrOS shelf: switch to feature mechanism and enable by default
>
> Fix a lot of tests that hardcode the size of the shelf.
>
> Bug: 871846
> Change-Id: I586da09835f03beb3e92712fbf32ebefd521a5d5
> Reviewed-on: https://chromium-review.googlesource.com/1188848
> Commit-Queue: Manu Cornet <manucornet@chromium.org>
> Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
> Reviewed-by: Alex Newcomer <newcomer@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#587038}

Bug: 871846, 878952 
Change-Id: Iafe30ae18feb8b5dc6f7ba11c367ea8a0651e840
Reviewed-on: https://chromium-review.googlesource.com/1197402
Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Manu Cornet <manucornet@chromium.org>
Cr-Commit-Position: refs/heads/master@{#587759}
[modify] https://crrev.com/a76b6b005860e9cec83f751e6c2ae0daff0a21b5/ash/accessibility/accessibility_panel_layout_manager_unittest.cc
[modify] https://crrev.com/a76b6b005860e9cec83f751e6c2ae0daff0a21b5/ash/app_list/home_launcher_gesture_handler_unittest.cc
[modify] https://crrev.com/a76b6b005860e9cec83f751e6c2ae0daff0a21b5/ash/dip_unittest.cc
[modify] https://crrev.com/a76b6b005860e9cec83f751e6c2ae0daff0a21b5/ash/display/display_move_window_util_unittest.cc
[modify] https://crrev.com/a76b6b005860e9cec83f751e6c2ae0daff0a21b5/ash/display/window_tree_host_manager_unittest.cc
[modify] https://crrev.com/a76b6b005860e9cec83f751e6c2ae0daff0a21b5/ash/extended_desktop_unittest.cc
[modify] https://crrev.com/a76b6b005860e9cec83f751e6c2ae0daff0a21b5/ash/magnifier/docked_magnifier_controller_unittest.cc
[modify] https://crrev.com/a76b6b005860e9cec83f751e6c2ae0daff0a21b5/ash/public/cpp/app_list/app_list_config.cc
[modify] https://crrev.com/a76b6b005860e9cec83f751e6c2ae0daff0a21b5/ash/root_window_controller_unittest.cc
[modify] https://crrev.com/a76b6b005860e9cec83f751e6c2ae0daff0a21b5/ash/screen_util_unittest.cc
[modify] https://crrev.com/a76b6b005860e9cec83f751e6c2ae0daff0a21b5/ash/shelf/overflow_bubble_view.cc
[modify] https://crrev.com/a76b6b005860e9cec83f751e6c2ae0daff0a21b5/ash/shelf/shelf_background_animator_unittest.cc
[modify] https://crrev.com/a76b6b005860e9cec83f751e6c2ae0daff0a21b5/ash/shelf/shelf_layout_manager_unittest.cc
[modify] https://crrev.com/a76b6b005860e9cec83f751e6c2ae0daff0a21b5/ash/shelf/shelf_view.cc
[modify] https://crrev.com/a76b6b005860e9cec83f751e6c2ae0daff0a21b5/ash/shelf/shelf_view_unittest.cc
[modify] https://crrev.com/a76b6b005860e9cec83f751e6c2ae0daff0a21b5/ash/shelf/shelf_widget_unittest.cc
[modify] https://crrev.com/a76b6b005860e9cec83f751e6c2ae0daff0a21b5/ash/wm/drag_window_resizer_unittest.cc
[modify] https://crrev.com/a76b6b005860e9cec83f751e6c2ae0daff0a21b5/ash/wm/lock_action_handler_layout_manager_unittest.cc
[modify] https://crrev.com/a76b6b005860e9cec83f751e6c2ae0daff0a21b5/ash/wm/overview/window_selector_unittest.cc
[modify] https://crrev.com/a76b6b005860e9cec83f751e6c2ae0daff0a21b5/ash/wm/window_positioner_unittest.cc
[modify] https://crrev.com/a76b6b005860e9cec83f751e6c2ae0daff0a21b5/ash/wm/window_state_unittest.cc
[modify] https://crrev.com/a76b6b005860e9cec83f751e6c2ae0daff0a21b5/ash/wm/window_util_unittest.cc
[modify] https://crrev.com/a76b6b005860e9cec83f751e6c2ae0daff0a21b5/ash/wm/workspace/multi_window_resize_controller_unittest.cc
[modify] https://crrev.com/a76b6b005860e9cec83f751e6c2ae0daff0a21b5/ash/wm/workspace/workspace_layout_manager_unittest.cc
[modify] https://crrev.com/a76b6b005860e9cec83f751e6c2ae0daff0a21b5/chrome/browser/about_flags.cc
[modify] https://crrev.com/a76b6b005860e9cec83f751e6c2ae0daff0a21b5/chromeos/chromeos_switches.cc
[modify] https://crrev.com/a76b6b005860e9cec83f751e6c2ae0daff0a21b5/chromeos/chromeos_switches.h
[modify] https://crrev.com/a76b6b005860e9cec83f751e6c2ae0daff0a21b5/tools/metrics/histograms/enums.xml