Revert r333104: "Added UMA statistics for changing the active window via click or touch events."

Revert r333104: "Added UMA statistics for changing the active window via click or touch events."

This caused leaks in the ChromeOS valgrind bot: http://build.chromium.org/p/chromium.memory.fyi/builders/Chromium%20OS%20%28valgrind%29%283%29/builds/37831/steps/memory%20test%3A%20ash_unittests/logs/stdio

Leak_DefinitelyLost
712 (136 direct, 576 indirect) bytes in 1 blocks are definitely lost in loss record 3,508 of 4,428
  operator new(unsigned long) (m_replacemalloc/vg_replace_malloc.c:1140)
  ash::(anonymous namespace)::DesktopTaskSwitchMetricRecorderTest::CreateNonPositionableWindow() const (ash/metrics/desktop_task_switch_metric_recorder_unittest.cc:113)
  ash::(anonymous namespace)::DesktopTaskSwitchMetricRecorderTest_ActivateNonPositionableWindowBetweenTwoPositionableWindowActivations_Test::TestBody() (ash/metrics/desktop_task_switch_metric_recorder_unittest.cc:189)

BUG=489813, 489814
TBR=bruthig@chromium.org

Committed: https://crrev.com/580afd414f1ba102a53eaa39bc670737efd4b3a6
Cr-Commit-Position: refs/heads/master@{#333185}

[Jeffrey Yasskin, 2015-06-05 23:17:29]

The CQ bit was checked by jyasskin@chromium.org

[commit-bot: I haz the power, 2015-06-05 23:18:45]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1165003010/1

[commit-bot: I haz the power, 2015-06-06 00:25:30]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-06 00:26:21]

Patchset 1 (id:??) landed as
https://crrev.com/580afd414f1ba102a53eaa39bc670737efd4b3a6
Cr-Commit-Position: refs/heads/master@{#333185}