Make FrameDestructionObserver::m_frame a private.

Make FrameDestructionObserver::m_frame a private.

Restrict visibility over FrameDestructionObserver, notably turning m_frame
into a private. This makes it slightly easier to replace
FrameDestructionObserver with something LifecycleObserver-derived instead.

Also includes some incidental core/plugins/ code tidyups.

R=haraken

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=190230

[sof, 2015-02-16 08:00:44]

sigbjornf@opera.com changed reviewers:
+ haraken@chromium.org

[sof, 2015-02-16 08:00:45]

Please take a look.

[haraken, 2015-02-16 08:11:33]

LGTM

[sof, 2015-02-16 08:18:22]

The CQ bit was checked by sigbjornf@opera.com

[commit-bot: I haz the power, 2015-02-16 08:19:21]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/928033002/1

[commit-bot: I haz the power, 2015-02-16 08:22:58]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=190230