Remove WebViewImpl preferred size hack

Remove WebViewImpl preferred size hack

In r193218, we changed scrollWidth/Height to return rounded
instead of truncated values, and I added a hack to WebViewImpl
to maintain the old behavior and not conflate that change with
the DOM api change. The old behavior is actually buggy and ends
up with the viewport size sometimes being off by a few pixels
when there's zooming. This patch removes the hack in WebViewImpl
and updates WebViewTest to this new behavior.

BUG=471336
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=193401

[leviw_travelin_and_unemployed, 2015-04-06 23:11:07]

leviw@chromium.org changed reviewers:
+ kalman@chromium.org, paulmeyer@chromium.org, pdr@chromium.org

[pdr., 2015-04-06 23:13:04]

LGTM!

[not at google - send to devlin, 2015-04-06 23:38:33]

Thanks Levi (my lgtm doesn't do anything).

[paulmeyer, 2015-04-07 12:25:19]

On 2015/04/06 23:38:33, kalman wrote:
> Thanks Levi (my lgtm doesn't do anything).

Lgtm.

[leviw_travelin_and_unemployed, 2015-04-07 23:57:33]

The CQ bit was checked by leviw@chromium.org

[leviw_travelin_and_unemployed, 2015-04-07 23:57:33]

The patchset sent to the CQ was uploaded after l-g-t-m from pdr@chromium.org,
paulmeyer@chromium.org, kalman@chromium.org
Link to the patchset: https://codereview.chromium.org/1061153002/#ps20001
(title: "Fix test")

[commit-bot: I haz the power, 2015-04-07 23:57:57]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1061153002/20001

[commit-bot: I haz the power, 2015-04-08 01:06:32]

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

[commit-bot: I haz the power, 2015-04-08 01:06:33]

Try jobs failed on following builders:
  mac_blink_rel on tryserver.blink (JOB_FAILED,
http://build.chromium.org/p/tryserver.blink/builders/mac_blink_rel/builds/50862)

[leviw_travelin_and_unemployed, 2015-04-08 22:09:37]

The CQ bit was checked by leviw@chromium.org

[leviw_travelin_and_unemployed, 2015-04-08 22:09:38]

The patchset sent to the CQ was uploaded after l-g-t-m from pdr@chromium.org,
paulmeyer@chromium.org, kalman@chromium.org
Link to the patchset: https://codereview.chromium.org/1061153002/#ps40001
(title: "Use Flexbox to avoid whitespace issue")

[commit-bot: I haz the power, 2015-04-08 22:10:54]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1061153002/40001

[commit-bot: I haz the power, 2015-04-09 00:15:50]

Committed patchset #3 (id:40001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=193401