Revert 237843 "Revert 237833 "[Telemetry] Attempt to fix flaky j..."

tonyg@ says this test is just flaky, so I'm reverting the revert.

BUG=247476,323249

> Revert 237833 "[Telemetry] Attempt to fix flaky jsgamebench time..."
> 
> [ RUN      ] ScrollActionTest.testScrollAction
> Traceback (most recent call last):
>   File "E:\b\build\slave\Win_7_Tests_x64__3_\build\src\tools\telemetry\telemetry\page\actions\scroll_unittest.py", line 66, in testScrollAction
>     (scroll_position, scroll_height))
> AssertionError: scroll_position=1427; scroll_height=1429
> 
> [  FAILED  ] ScrollActionTest.testScrollAction (3538 ms)
> 
> > [Telemetry] Attempt to fix flaky jsgamebench timeouts.
> > 
> > This benchmark can take 30 mins to run, but the buildbot times out after 20 mins
> > of no output. So raise its timeout and change WaitFor to output a heartbeat so
> > that the buildbot is happy with longer timeouts.
> > 
> > BUG=247476
> > 
> > Review URL: https://codereview.chromium.org/95513003
> 
> TBR=tonyg@chromium.org
> 
> Review URL: https://codereview.chromium.org/95793002

TBR=dbeam@chromium.org

Review URL: https://codereview.chromium.org/95853002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@237845 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 237845