Here is a failure stack trace, cc-ing csharrison@ who added this test recently:


../../base/test/metrics/histogram_tester.cc:202: Failure
Expected equality of these values:
  expected_count
    Which is: 1
  actual_count
    Which is: 0
Histogram "Navigation.DownloadPolicy" does not have the right number of samples (1) in the expected bucket (3). It has (0).
Stack trace:
#0 0x55fd67ca3960 StackTraceGetter::CurrentStackTrace()
#1 0x55fd67cc9027 testing::internal::UnitTestImpl::CurrentOsStackTraceExceptTop()
#2 0x55fd67cc8483 testing::internal::AssertHelper::operator=()
#3 0x55fd68d77658 base::HistogramTester::CheckBucketCount()
#4 0x55fd68d7742e base::HistogramTester::ExpectUniqueSample()
#5 0x55fd6737d559 base::HistogramTester::ExpectUniqueSample<>()
#6 0x55fd67376ddf content::NavigationBrowserTest_OpenerNavigation_DownloadPolicy_Test::RunTestOnMainThread()
#7 0x55fd68c731ad content::BrowserTestBase::ProxyRunTestOnMainThreadLoop()
#8 0x55fd66ec7f0d _ZN4base8internal13FunctorTraitsIMN7content41GenerateMHTMLAndExitRendererMessageFilterEFvvEvE6InvokeIS5_PS3_JEEEvT_OT0_DpOT1_
#9 0x55fd66ec7e84 _ZN4base8internal12InvokeHelperILb0EvE8MakeItSoIMN7content41GenerateMHTMLAndExitRendererMessageFilterEFvvEJPS5_EEEvOT_DpOT0_
#10 0x55fd66ec7e35 _ZN4base8internal7InvokerINS0_9BindStateIMN7content41GenerateMHTMLAndExitRendererMessageFilterEFvvEJNS0_17UnretainedWrapperIS4_EEEEEFvvEE7RunImplIS6_NSt3__15tupleIJS8_EEEJLm0EEEEvOT_OT0_NSD_16integer_sequenceImJXspT1_EEEE
#11 0x55fd670a3f9c _ZN4base8internal7InvokerINS0_9BindStateIMNS_12MockCallbackINS_17RepeatingCallbackIFvvEEEEEFvvEJNS0_17UnretainedWrapperIS7_EEEEES5_E3RunEPNS0_13BindStateBaseE
#12 0x55fd66d6727d _ZNKR4base17RepeatingCallbackIFvvEE3RunEv
#13 0x55fd68eedd4d content::ShellBrowserMainParts::PreMainMessageLoopRun()
#14 0x7f00aa30fc62 content::BrowserMainLoop::PreMainMessageLoopRun()
#15 0x7f00a8efff9d _ZN4base8internal13FunctorTraitsIMN7content12ChildProcessEFvvEvE6InvokeIS5_PS3_JEEEvT_OT0_DpOT1_
#16 0x7f00a8efff14 _ZN4base8internal12InvokeHelperILb0EvE8MakeItSoIMN7content12ChildProcessEFvvEJPS5_EEEvOT_DpOT0_
#17 0x7f00a8effec5 _ZN4base8internal7InvokerINS0_9BindStateIMN7content12ChildProcessEFvvEJNS0_17UnretainedWrapperIS4_EEEEEFvvEE7RunImplIS6_NSt3__15tupleIJS8_EEEJLm0EEEEvOT_OT0_NSD_16integer_sequenceImJXspT1_EEEE
#18 0x7f00a8f02e6c _ZN4base8internal7InvokerINS0_9BindStateIMN7content14ServiceFactoryEFvvEJNS0_17UnretainedWrapperIS4_EEEEEFvvEE3RunEPNS0_13BindStateBaseE
#19 0x7f00a8e0270d _ZNKR4base17RepeatingCallbackIFvvEE3RunEv
#20 0x7f00ab1e572d content::StartupTaskRunner::RunAllTasksNow()
#21 0x7f00aa30ba62 content::BrowserMainLoop::CreateStartupTasks()
#22 0x7f00aa317b63 content::BrowserMainRunnerImpl::Initialize()
#23 0x55fd68eecc98 ShellBrowserMain()
#24 0x55fd68e1364e content::ShellMainDelegate::RunProcess()
#25 0x7f00ac323d9a content::RunBrowserProcessMain()
#26 0x7f00ac326ad3 content::ContentMainRunnerImpl::Run()
#27 0x7f00ac31cafc content::ContentServiceManagerMainDelegate::RunEmbedderProcess()
#28 0x7f00895e3c2a service_manager::Main()
#29 0x7f00ac3214f3 content::ContentMain()
#30 0x55fd68c726d6 content::BrowserTestBase::SetUp()
#31 0x55fd68c4bd18 content::ContentBrowserTest::SetUp()
#32 0x55fd679ffe3e _ZN7testing8internal12InvokeHelperIvNSt3__15tupleIJEEEE12InvokeMethodIN4base7RunLoopEMS8_FvvEEEvPT_T0_RKS4_

To help debug, you can instrument GetDownloadPolicy in render_frame_impl.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/7fdc25a1a8cf3f82ca0ca4ab02fbe64de4bc5d16

commit 7fdc25a1a8cf3f82ca0ca4ab02fbe64de4bc5d16
Author: Mustaq Ahmed <mustaq@google.com>
Date: Mon Nov 19 20:38:04 2018

Remove unintended user activation in OpenerNavigation_DownloadPolicy

This fixes the test for UAv2.

Bug:  906639 
Change-Id: Ic23f0384691b4cbc3936efabafa2c8cbd128c780
Reviewed-on: https://chromium-review.googlesource.com/c/1342773
Reviewed-by: Charlie Harrison <csharrison@chromium.org>
Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Commit-Queue: Mustaq Ahmed <mustaq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609417}
[modify] https://crrev.com/7fdc25a1a8cf3f82ca0ca4ab02fbe64de4bc5d16/content/browser/navigation_browsertest.cc