[Android] Isolate OverscrollRefresh from device density

[Android] Isolate OverscrollRefresh from device density

Make the OverscrollRefresh effect take the target drag threshold as a
parameter. This isolates it from direct dependencies on the device scale
factor, making associated unit tests determnistics across all devices.

BUG=435125
Committed: https://crrev.com/d28baa33b8dcc3c0c8f9f23e008200bc0464d0af
Cr-Commit-Position: refs/heads/master@{#305026}

[whywhat, 2014-11-20 16:29:53]

avayvod@chromium.org changed reviewers:
+ avayvod@chromium.org

[whywhat, 2014-11-20 16:29:53]

lgtm

[jdduke (slow), 2014-11-20 16:37:43]

The CQ bit was checked by jdduke@chromium.org

[commit-bot: I haz the power, 2014-11-20 16:38:58]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/748433002/1

[commit-bot: I haz the power, 2014-11-20 17:27:34]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-11-20 17:28:08]

Patchset 1 (id:??) landed as
https://crrev.com/d28baa33b8dcc3c0c8f9f23e008200bc0464d0af
Cr-Commit-Position: refs/heads/master@{#305026}