Failing all over this tryserver:
https://ci.chromium.org/buildbot/tryserver.chromium.win/win10_chromium_x64_rel_ng/?limit=200

Just one example failure:
https://ci.chromium.org/buildbot/tryserver.chromium.win/win10_chromium_x64_rel_ng/29792

This is causing nearly every job to be retried. This is an emergency and must be fixed immediately.

Log excerpt follows.

[ RUN      ] DumpAccessibilityEventsTest.AccessibilityEventsLiveRegionRemove
[3352:4000:1117/162004.983:ERROR:instance.cc(49)] Unable to locate service manifest for metrics
[3352:4000:1117/162004.983:ERROR:service_manager.cc(889)] Failed to resolve service name: metrics
DevTools listening on ws://127.0.0.1:58303/devtools/browser/8e2a8fad-a3ea-46e6-91fa-c0500491f8e1
[4932:4088:1117/162005.169:INFO:dxva_video_decode_accelerator_win.cc(1295)] mf.dll is required for hardware video decoding
[4932:4088:1117/162005.169:INFO:media_foundation_video_encode_accelerator_win.cc(376)] mf.dll is required for encoding
[3352:4000:1117/162005.170:ERROR:instance.cc(49)] Unable to locate service manifest for metrics
[3352:4000:1117/162005.170:ERROR:service_manager.cc(889)] Failed to resolve service name: metrics
[3352:5048:1117/162005.347:INFO:dump_accessibility_browsertest_base.cc(225)] File not found: C:\b\s\w\ir\content\test\data\accessibility\event\live-region-remove-expected-blink.txt
[3352:5048:1117/162005.347:INFO:dump_accessibility_browsertest_base.cc(226)] No expectation file present, ignoring test on this platform. To run this test anyway, create C:\b\s\w\ir\content\test\data\accessibility\event\live-region-remove-expected-blink.txt (it can be empty) and then run content_browsertests with the switch: --generate-accessibility-test-expectations
[3352:5048:1117/162005.362:INFO:dump_accessibility_browsertest_base.cc(240)] Testing: C:/b/s/w/ir/content/test/data/accessibility/event/live-region-remove.html
[3352:5048:1117/162005.362:INFO:dump_accessibility_browsertest_base.cc(242)] Expected output: C:/b/s/w/ir/content/test/data/accessibility/event/live-region-remove-expected-win.txt
../../content/browser/accessibility/dump_accessibility_browsertest_base.cc(371): error: Value of: is_different
  Actual: true
Expected: false
Initial accessibility tree (after load complete):
ROLE_SYSTEM_DOCUMENT parent='ROLE_SYSTEM_WINDOW' window_class='Chrome_RenderWidgetHostHWND' value='http://127.0.0.1:58304/accessibility/event/live-region-remove.html' FOCUSED READONLY FOCUSABLE tag:#document offset:0 auto-generated:false background-color:rgb(255\,255\,255) color:rgb(0\,0\,0) font-family:Times New Roman font-size:12pt font-style:normal font-weight:normal invalid:false language:en-US text-line-through-mode:continuous text-line-through-style:none text-line-through-text: text-line-through-type:none text-line-through-width:auto text-outline:false text-position:baseline text-shadow:none text-underline-mode:continuous text-underline-style:none text-underline-type:none text-underline-width:auto writing-mode:lr ia2_hypertext='<obj0>' location=(0, 0) size=(800, 600) n_relations=0 n_characters=1 n_selections=0
++IA2_ROLE_SECTION parent='ROLE_SYSTEM_DOCUMENT' window_class='Chrome_RenderWidgetHostHWND' display:block tag:div live:polite relevant:additions text atomic:false container-live:polite container-relevant:additions text container-atomic:false container-busy:false id:live offset:0 auto-generated:false background-color:rgb(255\,255\,255) color:rgb(0\,0\,0) font-family:Times New Roman font-size:12pt font-style:normal font-weight:normal invalid:false language:en-US text-line-through-mode:continuous text-line-through-style:none text-line-through-text: text-line-through-type:none text-line-through-width:auto text-outline:false text-position:baseline text-shadow:none text-underline-mode:continuous text-underline-style:none text-underline-type:none text-underline-width:auto writing-mode:lr ia2_hypertext='<obj0>' location=(8, 16) size=(784, 18) index_in_parent=0 n_relations=0 n_characters=1 n_selections=0
++++IA2_ROLE_PARAGRAPH parent='DIV' window_class='Chrome_RenderWidgetHostHWND' display:block tag:p relevant:additions text atomic:false container-live:polite container-relevant:additions text container-atomic:false container-busy:false id:p offset:0 auto-generated:false background-color:rgb(255\,255\,255) color:rgb(0\,0\,0) font-family:Times New Roman font-size:12pt font-style:normal font-weight:normal invalid:false language:en-US text-line-through-mode:continuous text-line-through-style:none text-line-through-text: text-line-through-type:none text-line-through-width:auto text-outline:false text-position:baseline text-shadow:none text-underline-mode:continuous text-underline-style:none text-underline-type:none text-underline-width:auto writing-mode:lr ia2_hypertext='Before' location=(8, 16) size=(784, 18) index_in_parent=0 n_relations=0 n_characters=6 n_selections=0
++++++ROLE_SYSTEM_STATICTEXT name='Before' parent='P' window_class='Chrome_RenderWidgetHostHWND' display:block relevant:additions text atomic:false container-live:polite container-relevant:additions text container-atomic:false container-busy:false offset:0 auto-generated:false background-color:rgb(255\,255\,255) color:rgb(0\,0\,0) font-family:Times New Roman font-size:12pt font-style:normal font-weight:normal invalid:false language:en-US text-line-through-mode:continuous text-line-through-style:none text-line-through-text: text-line-through-type:none text-line-through-width:auto text-outline:false text-position:baseline text-shadow:none text-underline-mode:continuous text-underline-style:none text-underline-type:none text-underline-width:auto writing-mode:lr ia2_hypertext='Before' location=(8, 16) size=(44, 17) index_in_parent=0 n_relations=0 n_characters=6 n_selections=0
Final accessibility tree after events fired:
ROLE_SYSTEM_DOCUMENT parent='ROLE_SYSTEM_WINDOW' window_class='Chrome_RenderWidgetHostHWND' value='http://127.0.0.1:58304/accessibility/event/live-region-remove.html' FOCUSED READONLY FOCUSABLE tag:#document offset:0 auto-generated:false background-color:rgb(255\,255\,255) color:rgb(0\,0\,0) font-family:Times New Roman font-size:12pt font-style:normal font-weight:normal invalid:false language:en-US text-line-through-mode:continuous text-line-through-style:none text-line-through-text: text-lin[3352:5048:1117/162005.408:ERROR:dump_accessibility_browsertest_base.cc(396)] Diff:
* Line Expected
- ---- --------
     1 EVENT_OBJECT_HIDE on role=P
*    2 EVENT_OBJECT_STATECHANGE on role=DIV
*    3 IA2_EVENT_TEXT_REMOVED on role=DIV old_text={'<obj>' start=0 end=1}
*    4 EVENT_OBJECT_REORDER on role=DIV
*    5 EVENT_OBJECT_LIVEREGIONCHANGED on role=DIV
     6 <-- End-of-file -->
Actual
------
EVENT_OBJECT_HIDE on role=P
IA2_EVENT_TEXT_REMOVED on role=DIV old_text={'<obj>' start=0 end=1}
EVENT_OBJECT_REORDER on role=DIV
EVENT_OBJECT_LIVEREGIONCHANGED on role=DIV
<-- End-of-file -->
e-through-type:none text-line-through-width:auto text-outline:false text-position:baseline text-shadow:none text-underline-mode:continuous text-underline-style:none text-underline-type:none text-underline-width:auto writing-mode:lr ia2_hypertext='<obj0>' location=(0, 0) size=(800, 600) n_relations=0 n_characters=1 n_selections=0
++IA2_ROLE_SECTION parent='ROLE_SYSTEM_DOCUMENT' window_class='Chrome_RenderWidgetHostHWND' display:block tag:div live:polite relevant:additions text atomic:false container-live:polite container-relevant:additions text container-atomic:false container-busy:false id:live location=(8, 8) size=(784, 0) index_in_parent=0 n_relations=0 n_characters=0 n_selections=0
[  FAILED  ] DumpAccessibilityEventsTest.AccessibilityEventsLiveRegionRemove, where TypeParam =  and GetParam() =  (460 ms)