WebContentsViewAuraTest.VerticalOverscroll is flakey. It is relatively quick to repro locally if the `stress` utility is used in conjunction with running tests. See below for example commands.

Example bot failure: https://build.chromium.org/p/chromium.chromiumos/builders/Linux%20ChromiumOS%20Tests%20%28dbg%29%281%29/builds/20798

The best way I've found to repro is by running stress to load the host system and then running the test
$ stress -c 40 -i 40 -m 40 -d 40 -t 300
$ ./out/Release/content_browsertests --gtest_filter=WebContentsViewAuraTest.VerticalOverscroll --gtest_repeat=100
IMPORTANT DEBUGGING NOTE: each test is run inside its own process.
For debugging a test inside a debugger, use the
--gtest_filter=<your_test_name> flag along with either
--single_process (to run the test in one launcher/browser process) or
--single-process (to do the above, and also run Chrome in single-process mode).
Using sharding settings from environment. This is shard 0/1
Using 1 parallel jobs.
Note: Google Test filter = WebContentsViewAuraTest.VerticalOverscroll
[==========] Running 1 test from 1 test case.
[----------] Global test environment set-up.
[----------] 1 test from WebContentsViewAuraTest, where TypeParam =
[ RUN      ] WebContentsViewAuraTest.VerticalOverscroll
[2906:2930:1220/150223.313889:951153882595:ERROR:entry.cc(167)] Entry::Deserialize: dictionary has no interface_provider_specs key
[2906:2930:1220/150223.373743:951153942333:ERROR:entry.cc(167)] Entry::Deserialize: dictionary has no interface_provider_specs key
[2906:2930:1220/150223.376070:951153944657:ERROR:entry.cc(167)] Entry::Deserialize: dictionary has no interface_provider_specs key
Xlib:  extension "RANDR" missing on display ":99".
[2906:2906:1220/150223.394333:951153962924:ERROR:proxy_service.cc(1519)] ProxyConfigService for ChromeOS should be created in profile_io_data.cc::CreateProxyConfigService and this should be used only for examples.
libva info: VA-API version 0.35.0
libva info: va_getDriverName() returns -1
libva error: va_getDriverName() failed with unknown libva error,driver_name=(null)
[2931:2931:1220/150223.849143:951154417738:WARNING:vaapi_wrapper.cc(1224)] vaInitialize failed: unknown libva error
../../content/browser/web_contents/web_contents_view_aura_browsertest.cc:1087: Failure
Expected: (0) < (tracker.num_overscroll_updates()), actual: 0 vs 0
../../content/browser/web_contents/web_contents_view_aura_browsertest.cc:1088: Failure
Value of: tracker.overscroll_completed()
  Actual: false
Expected: true
[  FAILED  ] WebContentsViewAuraTest.VerticalOverscroll, where TypeParam =  and GetParam() =  (4762 ms)
[----------] 1 test from WebContentsViewAuraTest (4762 ms total)

[----------] Global test environment tear-down
[==========] 1 test from 1 test case ran. (4763 ms total)
[  PASSED  ] 0 tests.
[  FAILED  ] 1 test, listed below:
[  FAILED  ] WebContentsViewAuraTest.VerticalOverscroll, where TypeParam =  and GetParam() =

 1 FAILED TEST
[1220/150227.584009:ERROR:kill_posix.cc(84)] Unable to terminate process group 2906: No such process
[1/1] WebContentsViewAuraTest.VerticalOverscroll (5286 ms)