Add tests for resizing VPX larger than initial size

Add tests for resizing VPX larger than initial size.

libvpx/VP8 currently allows resizing upward but will crash on codec
teardown in that case; these tests ensure we don't regress when we
remove the workarounds in VideoEncoderVpx.

BUG=134202
Committed: https://crrev.com/ae4b5eecd062dc4d28356b9925752ca52f53c46c
Cr-Commit-Position: refs/heads/master@{#313741}

[Wez, 2015-01-27 21:28:51]

wez@chromium.org changed reviewers:
+ sergeyu@chromium.org

[Wez, 2015-01-27 21:28:51]

PTAL

[Sergey Ulanov, 2015-01-28 06:54:55]

lgtm

[Wez, 2015-01-29 18:24:00]

The CQ bit was checked by wez@chromium.org

[commit-bot: I haz the power, 2015-01-29 18:24:23]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/866533004/1

[commit-bot: I haz the power, 2015-01-29 18:32:46]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-01-29 18:33:53]

Patchset 1 (id:??) landed as
https://crrev.com/ae4b5eecd062dc4d28356b9925752ca52f53c46c
Cr-Commit-Position: refs/heads/master@{#313741}