Parameterize PinchViewportTest for root layer scrolling.

Parameterize PinchViewportTest for root layer scrolling.

This is similar to what http://crrev.com/1155313003 did for WebFrameTest.

Some test cases already pass, and some are fixed here by updating the test to
use layoutViewportScrollableArea() instead of directly accessing the FrameView.

A few test cases fail non-trivially; they remain un-parameterized here, and
will be addressed in later patches.

BUG=490942
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=197775

[skobes, 2015-06-24 18:58:50]

Patchset #1 (id:1) has been deleted

[skobes, 2015-06-24 18:58:56]

Patchset #1 (id:20001) has been deleted

[skobes, 2015-06-24 18:59:02]

Patchset #1 (id:40001) has been deleted

[skobes, 2015-06-24 19:47:06]

skobes@chromium.org changed reviewers:
+ dsinclair@chromium.org

[skobes, 2015-06-24 19:47:07]

(Thanks to szager for starting the patch.)

[dsinclair, 2015-06-24 19:55:18]

The CQ bit was checked by dsinclair@chromium.org

[dsinclair, 2015-06-24 19:55:19]

lgtm

[commit-bot: I haz the power, 2015-06-24 19:55:40]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1205103003/60001

[commit-bot: I haz the power, 2015-06-24 20:11:37]

Committed patchset #1 (id:60001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=197775