Revert of Don't treat first touch move differently from future touch moves

Revert of Don't treat first touch move differently from future touch moves (https://codereview.chromium.org/228973003/)

Reason for revert:
This never set |seen_scroll_update_this_sequence_| to true, resulting in:
https://code.google.com/p/chromium/issues/detail?id=393695

The fact that no tests caught this issue is pretty scary; we'll need some beefier tests as well as the trivial fix.

Original issue's description:
> Don't treat first move touch differently from future touch moves.
> 
> See http://lists.w3.org/Archives/Public/public-touchevents/2014Apr/0005.html for details.
> 
> BUG=354460
> TEST=TouchEventQueueTest.TouchAbsorptionWithConsumedFirstMove, TouchEventQueueTest.TouchCancelOnScroll
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=282642

TBR=jdduke, sadrul

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=283089

[tdresser, 2014-07-14 20:35:33]

Created Revert of Don't treat first touch move differently from future touch
moves

[commit-bot: I haz the power, 2014-07-14 20:37:29]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/tdresser@chromium.org/394523004/1

[commit-bot: I haz the power, 2014-07-14 20:37:30]

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

[commit-bot: I haz the power, 2014-07-14 20:37:30]

No LGTM from a valid reviewer yet. Only full committers are accepted.
Even if an LGTM may have been provided, it was from a non-committer or
a provisional committer, _not_ a full super star committer.
See http://www.chromium.org/getting-involved/become-a-committer
Note that this has nothing to do with OWNERS files.

[tdresser, 2014-07-14 20:44:41]

The CQ bit was checked by tdresser@chromium.org

[commit-bot: I haz the power, 2014-07-14 20:45:09]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/tdresser@chromium.org/394523004/1

[commit-bot: I haz the power, 2014-07-14 23:55:07]

Change committed as 283089