[Telemetry] Remove empty_action_name_to_run for tab_switching

[Telemetry] Remove empty_action_name_to_run for tab_switching

Remove scrolling action for pages of Top10PageSet.
Measurements that are paired with Top10PageSet are
TabSwitching & PageCycler.  Both of these originally set
action_name_to_run='' which means that they don't expect
RunPageInteraction to run anything.

BUG=418375
Committed: https://crrev.com/b83bcccc6666071524a10d46c36aa25e83f15a19
Cr-Commit-Position: refs/heads/master@{#313534}

[nednguyen, 2015-01-28 00:11:15]

Patchset #1 (id:1) has been deleted

[nednguyen, 2015-01-28 00:16:02]

nednguyen@google.com changed reviewers:
+ dtu@chromium.org, sullivan@chromium.org

[sullivan, 2015-01-28 03:56:35]

lgtm

[nednguyen, 2015-01-28 16:01:03]

The CQ bit was checked by nednguyen@google.com

[commit-bot: I haz the power, 2015-01-28 16:01:55]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/885493004/20001

[commit-bot: I haz the power, 2015-01-28 17:19:42]

Committed patchset #1 (id:20001)

[commit-bot: I haz the power, 2015-01-28 17:21:24]

Patchset 1 (id:??) landed as
https://crrev.com/b83bcccc6666071524a10d46c36aa25e83f15a19
Cr-Commit-Position: refs/heads/master@{#313534}