Revert of Do not interchange MOUSE_MOVED and MOUSE_DRAGGED events in Widget

Revert of Do not interchange MOUSE_MOVED and MOUSE_DRAGGED events in Widget (patchset #8 id:140001 of https://codereview.chromium.org/560053002/)

Reason for revert:
Responsible for the crash reported in crbug.com/430427. Relanding will require addressing crbug.com/431350 first.

Original issue's description:
> Do not interchange MOUSE_MOVED and MOUSE_DRAGGED events in Widget
>
> In Widget::OnMouseEvent(), do not handle MOUSE_MOVED
> events as MOUSE_DRAGGED events, and do not handle
> MOUSE_DRAGGED events as MOUSE_MOVED events; instead
> trust that the mouse event type has been set correctly
> before arriving at Widget. This also allows us to
> remove the member |is_mouse_button_pressed_|
> from Widget.
>
> BUG=412929, 412931
> TEST=WidgetTest.DragIntoView

BUG=412929, 412931
TBR=sadrul@chromium.org

Committed: https://crrev.com/f2d6fd8f14b22b4b15e5e8fd3ac2bb8141bef552
Cr-Commit-Position: refs/heads/master@{#303274}

[tdanderson, 2014-11-07 18:28:27]

Created Revert of Do not interchange MOUSE_MOVED and MOUSE_DRAGGED events in
Widget

[tdanderson, 2014-11-07 18:58:30]

The CQ bit was checked by tdanderson@chromium.org

[commit-bot: I haz the power, 2014-11-07 18:59:32]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/703643004/1

[commit-bot: I haz the power, 2014-11-07 19:49:12]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-11-07 19:50:11]

Patchset 1 (id:??) landed as
https://crrev.com/f2d6fd8f14b22b4b15e5e8fd3ac2bb8141bef552
Cr-Commit-Position: refs/heads/master@{#303274}