Revert of Revert of Fixes dragging to be less likely to trigger false positive switch to docking

Revert of Revert of Adjusts dragging logic to be less likely to trigger false positive switch from snapping to docking (patchset #1 id:1 of https://codereview.chromium.org/1128933005/)

Reason for revert:
This revert probably did not fix the flakiness. I suspect that a revert that actually ended up fixing the bots is this: https://codereview.chromium.org/1139943002.

I will re-land my original change.

Original issue's description:
> Revert of Adjusts dragging logic to be less likely to trigger false positive switch from snapping to docking (patchset #5 id:90001 of https://codereview.chromium.org/1127133003/)
>
> Reason for revert:
> I suspect this is causing a browser_tests failure on the bots:
>
> http://build.chromium.org/p/chromium.chromiumos/builders/Linux%20ChromiumOS%20Tests%20%28dbg%29%281%29/builds/2069
> https://build.chromium.org/p/chromium.webkit/builders/Linux%20ChromiumOS%20Tests%20%28dbg%29%281%29/builds/1913
>
> Sorry!
>
> Original issue's description:
> > Adjusts dragging logic to be less likely to trigger false positive switch from
> > snapping to docking.
> >
> > This CL adjusts the logic which selects whether a window will be snapped to
> > half of the workspace width or will be docked at the end of the drag when the
> > window is dragged to the edge of the workspace in the special case of the dock
> > being visible. The CL makes it easier to snap a window to half the workspace
> > width in this special case (and harder to inadvertently dock the window)
> >
> > BUG=484877
> > TEST=None
> >
> > Committed: https://crrev.com/988c697aff35b3fd347dec35f2f2ac159c8328a9
> > Cr-Commit-Position: refs/heads/master@{#329268}
>
> TBR=pkotwicz@chromium.org,varkha@chromium.org
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=484877
>
> Committed: https://crrev.com/0d4f7d597774f7415f1aff374db498c8fbe88a9a
> Cr-Commit-Position: refs/heads/master@{#329301}

TBR=pkotwicz@chromium.org,dpranke@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=484877
Committed: https://crrev.com/7c332249b80e021f0c4846c934dfd2f957e489d6
Cr-Commit-Position: refs/heads/master@{#329413}

[varkha, 2015-05-12 16:07:11]

Created Revert of Revert of Adjusts dragging logic to be less likely to trigger
false positive switch from snapping to docking

[varkha, 2015-05-12 16:07:40]

The CQ bit was checked by varkha@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-05-12 16:09:15]

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

[varkha, 2015-05-12 16:10:28]

The CQ bit was checked by varkha@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-05-12 16:10:55]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1140733002/1

[commit-bot: I haz the power, 2015-05-12 16:11:45]

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

[commit-bot: I haz the power, 2015-05-12 16:11:46]

Dry run: This issue passed the CQ dry run.

[varkha, 2015-05-12 16:13:07]

The CQ bit was checked by varkha@chromium.org

[commit-bot: I haz the power, 2015-05-12 16:13:33]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1140733002/1

[commit-bot: I haz the power, 2015-05-12 16:14:57]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-12 16:15:42]

Patchset 1 (id:??) landed as
https://crrev.com/7c332249b80e021f0c4846c934dfd2f957e489d6
Cr-Commit-Position: refs/heads/master@{#329413}

[Dirk Pranke, 2015-05-12 18:42:14]

lgtm