Revert "WPT Import: Trigger CQ dry run with initial try jobs"

This reverts commit e4d31059.

Reason for revert: This appears to cause the importer to not work quite right:

It seems to now print:
Triggering CQ try jobs.
Waiting for try jobs (timeout: 10800 seconds).
All jobs finished.
No CQ try job results, aborting.
step returned non-zero exit code: 1

https://luci-logdog.appspot.com/v/?s=chromium%2Fbb%2Fchromium.infra.cron%2Fwpt-importer%2F403%2F%2B%2Frecipes%2Fsteps%2FImport_changes_from_WPT_to_Chromium%2F0%2Fstdout

Original change's description:
> WPT Import: Trigger CQ dry run with initial try jobs
> 
> Reason: Currently, the shortest time that a import job can take is
> the time for two try job cycles (tryserver.blink try bots, then CQ
> try bots).
> 
> If we do frequent imports, then I would expect most imports to require
> no new expectations and only one patch set is needed. In this case
> (expected to be the common case) this will make imports about twice
> as fast.
> 
> As a proportion of total CQ load, this is not expected to put
> significant extra load on CQ.
> 
> Change-Id: Idac8e256c355affc26c1f4f69814a60154128684
> Reviewed-on: https://chromium-review.googlesource.com/590187
> Reviewed-by: Kent Tamura <tkent@chromium.org>
> Commit-Queue: Quinten Yearsley <qyearsley@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#490144}

TBR=qyearsley@chromium.org,tkent@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Change-Id: I6ec3052391fba8dfc634fa3f7029e9cee41675ea
Reviewed-on: https://chromium-review.googlesource.com/594691Reviewed-by: Quinten Yearsley <qyearsley@chromium.org>
Reviewed-by: Kent Tamura <tkent@chromium.org>
Commit-Queue: Quinten Yearsley <qyearsley@chromium.org>
Cr-Commit-Position: refs/heads/master@{#490833}

third_party/WebKit/Tools/Scripts/webkitpy/w3c/test_importer.py

@@ -143,12 +143,6 @@ class TestImporter(object):
         """
         _log.info('Triggering try jobs for updating expectations.')
         self.git_cl.trigger_try_jobs()
-
-        # If we also trigger a CQ dry run at this point and there are no
-        # new baselines or expectation lines required, then this will save
-        # us from having to wait for the CQ later on.
-        self.git_cl.run(['try'])
-
         try_results = self.git_cl.wait_for_try_jobs(
             poll_delay_seconds=POLL_DELAY_SECONDS,
             timeout_seconds=TIMEOUT_SECONDS)
@@ -169,9 +163,6 @@ class TestImporter(object):
 
     def run_commit_queue_for_cl(self):
         """Triggers CQ and either commits or aborts; returns True on success."""
-        # If a CQ dry was was previously done and no new patch was uploaded
-        # for test expectations, it's still OK to run `git cl try` again; no
-        # new unnecessary try jobs should be started.
         _log.info('Triggering CQ try jobs.')
         self.git_cl.run(['try'])
         try_results = self.git_cl.wait_for_try_jobs(