Revert of Re-enable memory.top_7_stress test now that bug 455349 is fixed.

Revert of Re-enable memory.top_7_stress test now that bug 455349 is fixed. (patchset #1 id:1 of https://codereview.chromium.org/940283007/)

Reason for revert:
This is failing on the bots.  Sample failure: http://build.chromium.org/p/chromium.perf/builders/Win%207%20Perf%20%283%29/builds/3899/steps/memory.top_7_stress.reference/logs/stdio#failure1

[ RUN      ] Facebook
INFO:root:Loading http://www.facebook.com/...
WARNING:root:Timed out while loading: http://www.facebook.com/
Traceback (most recent call last):
  File "...\telemetry\telemetry\user_story\user_story_runner.py", line 100, in _RunUserStoryAndProcessErrorIfNeeded
    state.RunUserStory(results)
  File "...\telemetry\telemetry\page\shared_page_state.py", line 240, in RunUserStory
    self._PreparePage()
  File "...\telemetry\telemetry\page\shared_page_state.py", line 223, in _PreparePage
    'Login as ' + self._current_page.credentials + ' failed')
Failure: Login as facebook failed

[ ... ]

[  FAILED  ] Facebook (60937 ms)

Original issue's description:
> Re-enable memory.top_7_stress test now that bug 455349 is fixed.
> 
> BUG=459646
> 
> Committed: https://crrev.com/92fb7ce426ebe966630fbd0de62e59cee91a6e74
> Cr-Commit-Position: refs/heads/master@{#317606}

TBR=petrcermak@chromium.org,primiano@chromium.org,sullivan@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=459646

[Ilya Sherman, 2015-02-23 23:04:02]

Created Revert of Re-enable memory.top_7_stress test now that bug 455349 is
fixed.

[commit-bot: I haz the power, 2015-02-23 23:05:48]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/951683003/1

[commit-bot: I haz the power, 2015-02-23 23:07:05]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-02-23 23:07:06]

Failed to apply the patch.

[commit-bot: I haz the power, 2015-02-23 23:08:11]

The CQ bit was unchecked by commit-bot@chromium.org