Findit identified the culprit r561175 with confidence 70.0% in the config "chromium.win / Win7 Tests (dbg)(1)"
based on the flakiness trend:

https://findit-for-me.appspot.com/waterfall/flake?key=ag9zfmZpbmRpdC1mb3ItbWVyywELEhdNYXN0ZXJGbGFrZUFuYWx5c2lzUm9vdCKUAWNocm9taXVtLndpbi9XaW43IFRlc3RzIChkYmcpKDEpLzY5Mzg4L3Zpel9jb250ZW50X2Jyb3dzZXJ0ZXN0cy9WMlZpVW5SalIyVjBWWE5sY2sxbFpHbGhRbkp2ZDNObGNsUmxjM1F1VTNKalQySnFaV04wVW1Wd2JHRmpaVWx1WVdOMGFYWmxWSEpoWTJ0ekx6RT0MCxITTWFzdGVyRmxha2VBbmFseXNpcxgBDA


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Feedback is welcome! Please use component Tools>Test>FindIt>Flakiness

[ RUN      ] WebRtcGetUserMediaBrowserTest.SrcObjectReplaceInactiveTracks/1


DevTools listening on ws://127.0.0.1:64247/devtools/browser/c07a02c3-2b10-4797-ab0a-e8e0e2b4562f
[8992:10396:0603/224930.529:INFO:media_foundation_video_encode_accelerator_win.cc(353)] Windows versions earlier than 8 are not supported.

From javascript: Error
    at failTest (http://127.0.0.1:64248/media/webrtc_test_utilities.js:30:17)
    at assertTrue (http://127.0.0.1:64248/media/webrtc_test_utilities.js:180:5)
    at HTMLVideoElement.video.onplaying (http://127.0.0.1:64248/media/getusermedia.html:556:9)
When executing 'srcObjectReplaceInactiveTracks()'
../../content/browser/webrtc/webrtc_content_browsertest_base.cc(95): error: Failed
Stack trace:
Backtrace:
	StackTraceGetter::CurrentStackTrace [0x01C5632A+90]
	testing::internal::UnitTestImpl::CurrentOsStackTraceExceptTop [0x01C6DAEA+74]
	testing::internal::AssertHelper::operator= [0x01C6D5FB+75]
	content::WebRtcContentBrowserTestBase::ExecuteJavascriptAndWaitForOk [0x0179EDAA+250]
	content::WebRtcGetUserMediaBrowserTest_SrcObjectReplaceInactiveTracks_Test::RunTestOnMainThread [0x017ADE50+592]
	content::BrowserTestBase::ProxyRunTestOnMainThreadLoop [0x02C65324+804]
	??$Invoke@P8BrowserTestBase@content@@AEXXZPAV12@$$V@?$FunctorTraits@P8BrowserTestBase@content@@AEXXZX@internal@base@@SAXP8BrowserTestBase@content@@AEXXZ$$QAPAV34@@Z [0x02C675EC+28]
	base::internal::InvokeHelper<0,void>::MakeItSo<void (__thiscall content::BrowserTestBase::*const &)(void),content::BrowserTestBase *> [0x02C6752F+79]
	base::internal::Invoker<base::internal::BindState<void (__thiscall content::BrowserTestBase::*)(void),base::internal::UnretainedWrapper<content::BrowserTestBase> >,void __cdecl(void)>::RunImpl<void (__thiscall content::BrowserTestBase::*const &)(void),std [0x02C674C5+85]
	base::internal::Invoker<base::internal::BindState<void (__thiscall content::BrowserTestBase::*)(void),base::internal::UnretainedWrapper<content::BrowserTestBase> >,void __cdecl(void)>::Run [0x02C673BF+63]
	base::RepeatingCallback<void __cdecl(void)>::Run [0x00F17AA2+50]
	content::ShellBrowserMainParts::PreMainMessageLoopRun [0x02F77CF5+101]
	content::BrowserMainLoop::PreMainMessageLoopRun [0x5FDBBCF6+342]
	??$Invoke@P8BrowserMainLoop@content@@AEHXZPAV12@$$V@?$FunctorTraits@P8BrowserMainLoop@content@@AEHXZX@internal@base@@SAHP8BrowserMainLoop@content@@AEHXZ$$QAPAV34@@Z [0x5FDC5E0C+28]
	base::internal::InvokeHelper<0,int>::MakeItSo<int (__thiscall content::BrowserMainLoop::*const &)(void),content::BrowserMainLoop *> [0x5FDC5D3F+79]
	base::internal::Invoker<base::internal::BindState<int (__thiscall content::BrowserMainLoop::*)(void),base::internal::UnretainedWrapper<content::BrowserMainLoop> >,int __cdecl(void)>::RunImpl<int (__thiscall content::BrowserMainLoop::*const &)(void),std::t [0x5FDC5CD5+85]
	base::internal::Invoker<base::internal::BindState<int (__thiscall content::BrowserMainLoop::*)(void),base::internal::UnretainedWrapper<content::BrowserMainLoop> >,int __cdecl(void)>::Run [0x5FDC5B8F+63]
	base::RepeatingCallback<int __cdecl(void)>::Run [0x60703362+50]
	content::StartupTaskRunner::RunAllTasksNow [0x61035BC9+137]
	content::BrowserMainLoop::CreateStartupTasks [0x5FDB99F5+1493]
	content::BrowserMainRunnerImpl::Initialize [0x5FDCBD8F+1983]
	content::BrowserMainRunnerImpl::Initialize [0x5FDCB5AD+93]
	ShellBrowserMain [0x035F6CB8+72]
	content::ShellMainDelegate::RunProcess [0x035EECEC+300]
	content::RunBrowserProcessMain [0x62642DE6+134]
	content::ContentMainRunnerImpl::Run [0x6264419A+618]
	content::ContentServiceManagerMainDelegate::RunEmbedderProcess [0x62640761+33]
	service_manager::Main [0x5D2B372A+1418]
	content::ContentMain [0x62642CDC+92]
	content::BrowserTestBase::SetUp [0x02C64BD1+2913]
	content::ContentBrowserTest::SetUp [0x02C3F737+135]
	content::WebRtcContentBrowserTestBase::SetUp [0x0179E7F2+34]

[11016:9072:0603/224933.078:INFO:user_input_monitor_win.cc(170)] RegisterRawInputDevices() failed for RIDEV_REMOVE: The parameter is incorrect. (0x57)
[11016:4316:0603/224933.144:WARNING:discardable_shared_memory_manager.cc(431)] Some MojoDiscardableSharedMemoryManagerImpls are still alive. They will be leaked.
[  FAILED  ] WebRtcGetUserMediaBrowserTest.SrcObjectReplaceInactiveTracks/1, where GetParam() = true (2900 ms)

WebRtcGetUserMediaBrowserTest.SrcObjectReplaceInactiveTracks/0 flakes with the same error (HTMLVideoElement.video.onplaying (http://127.0.0.1:64248/media/getusermedia.html:556:9))

Disabling test.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e02f90c7429501e3d2b0ec923d096b4b0428d4ec

commit e02f90c7429501e3d2b0ec923d096b4b0428d4ec
Author: Dominic Battre <battre@chromium.org>
Date: Mon Jun 04 12:17:39 2018

Disable flaky WebRtcGetUserMediaBrowserTest.SrcObjectReplaceInactiveTracks

TBR=guidou@chromium.org

Bug: 848330
Change-Id: I3bd40659880778b74a8daf415c5ac44e3306d6a9
Reviewed-on: https://chromium-review.googlesource.com/1084836
Reviewed-by: Dominic Battré <battre@chromium.org>
Reviewed-by: Guido Urdaneta <guidou@chromium.org>
Commit-Queue: Dominic Battré <battre@chromium.org>
Cr-Commit-Position: refs/heads/master@{#564063}
[modify] https://crrev.com/e02f90c7429501e3d2b0ec923d096b4b0428d4ec/content/browser/webrtc/webrtc_getusermedia_browsertest.cc

Changing priority to 2 since the test is disabled.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/2666f2b66a1f4954eff110c14e895976c6acf03d

commit 2666f2b66a1f4954eff110c14e895976c6acf03d
Author: Dominic Battre <battre@chromium.org>
Date: Wed Sep 19 07:38:33 2018

Fix typo in disabling a WebRtcGetUserMediaBrowserTest

Fix typo in disabling
WebRtcGetUserMediaBrowserTest.SrcObjectReplaceInactiveTracks

TBR=xiyuan@chromium.org

Bug: 848330
Change-Id: I13e2a7883b06a930bd0e6fe7e6f3cce9b3f0563f
Reviewed-on: https://chromium-review.googlesource.com/1233194
Reviewed-by: Dominic Battré <battre@chromium.org>
Commit-Queue: Dominic Battré <battre@chromium.org>
Cr-Commit-Position: refs/heads/master@{#592333}
[modify] https://crrev.com/2666f2b66a1f4954eff110c14e895976c6acf03d/content/browser/webrtc/webrtc_getusermedia_browsertest.cc