Failure detection. All are by uncommit patch.

I am not sure I understand. All 3 failures that were reported when this bug was filed (and a few more afterwards) come from different patches (CLs). The CLs in question do not look like they've introduced the flakiness, so most likely the flakiness comes from committed code. The fact that this test has been flaky in over 3 different CLs already makes it even more likely. IMHO, this is a valid flaky test that needs to be disabled and the issue needs to be assigned to an owner.

Please feel free to reach back to me if you have more questions.

Yes, Yoichi, these look to be real flakes and need to be investigated by sheriffs. Please see https://sites.google.com/a/chromium.org/dev/developers/tree-sheriffs/sheriffing-bug-queues#triaging-auto-filed-flakiness-bugs to understand how the system works and why these should not be ignored.

Trying this:
https://chromium-review.googlesource.com/c/523039/

Disable flickr_infinite_scroll

Failing still on multiple platforms.

Previous disabling in commit 6df637aba4c300a651cd8934f59bf8d48760f8ef
was not sufficient.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/0e0221f193ff2027ee5eaf39fb8e9b5f728a23b6

commit 0e0221f193ff2027ee5eaf39fb8e9b5f728a23b6
Author: Vincent Scheib <scheib@chromium.org>
Date: Sat Jun 03 03:03:57 2017

Disable twitter_infinite_scroll & flickr_infinite_scroll

Failing still on multiple platforms.

Previous disabled on only some platforms in
commit 6df637aba4c300a651cd8934f59bf8d48760f8ef
commit 851b9016ee273f0d3cef7eaab1cd2d1e58fc93a2

TBR=scheib@chromium.org

Bug:  728785 ,  728934 ,  724262 
Change-Id: I2cdccb0fa5e1f9287edd59ef2f0519284f3787f5
Reviewed-on: https://chromium-review.googlesource.com/523039
Commit-Queue: Vincent Scheib <scheib@chromium.org>
Reviewed-by: Ned Nguyen <nednguyen@google.com>
Reviewed-by: Vincent Scheib <scheib@chromium.org>
Cr-Commit-Position: refs/heads/master@{#476878}
[modify] https://crrev.com/0e0221f193ff2027ee5eaf39fb8e9b5f728a23b6/tools/perf/page_sets/system_health/expectations.py

Detected 6 new flakes for test/step "benchmarks.system_health_smoke_test.SystemHealthBenchmarkSmokeTest.system_health.memory_desktop.browse:media:flickr_infinite_scroll". To see the actual flakes, please visit https://chromium-try-flakes.appspot.com/all_flake_occurrences?key=ahVzfmNocm9taXVtLXRyeS1mbGFrZXNyjwELEgVGbGFrZSKDAWJlbmNobWFya3Muc3lzdGVtX2hlYWx0aF9zbW9rZV90ZXN0LlN5c3RlbUhlYWx0aEJlbmNobWFya1Ntb2tlVGVzdC5zeXN0ZW1faGVhbHRoLm1lbW9yeV9kZXNrdG9wLmJyb3dzZTptZWRpYTpmbGlja3JfaW5maW5pdGVfc2Nyb2xsDA. This message was posted automatically by the chromium-try-flakes app.

Now that these tests have been disabled on all platforms, they're no longer a sheriff issue.

It seems flickr has disabled infinite scrolling.
When I ran "tools/perf/record_wpr --browser=system desktop_common_system_health --story-filter=browse:media:flickr_infinite_scroll", I get

  File "/usr/local/google/home/xunjieli/chrome/src/tools/perf/page_sets/system_health/browsing_stories.py", line 808, in _DidLoadDocument
    self._Scroll(action_runner, self.SCROLL_DISTANCE, self.SCROLL_STEP)
  File "/usr/local/google/home/xunjieli/chrome/src/tools/perf/page_sets/system_health/browsing_stories.py", line 830, in _Scroll
    'Scrolling stuck at %d' % remaining)
StoryActionError: Scrolling stuck at 9929