Revert of Refactor frame navigation/detach state cleanup to be more sane.

Revert of Refactor frame navigation/detach state cleanup to be more sane. (patchset #13 id:230001 of https://codereview.chromium.org/1052993006/)

Reason for revert:
PasswordManagerBrowserTest.NoPromptForFailedLoginFromSubFrameWithMultiFramesInPage is broken by this change.

Original issue's description:
> Refactor frame navigation/detach state cleanup to be more sane.
> 
> Prior to this patch, cleaning up state for a navigating or detaching
> frame was ad hoc: often times, code to do the same thing (e.g. detach
> child frames) was present in multiple locations just to "be sure" that
> the cleanup would happen no matter what code path was taken.
> 
> This logic has been reorganized so that the state cleanup always follows
> a similar flow for both navigation and detach. There are now 4 common
> steps:
>   1. FrameLoader::dispatchUnloadEvent()
>   2. Frame::detachChildren()
>   3. Document::prepareForDestruction()
>   4. FrameLoader::clear()
> 
> BUG=464764
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=193157

TBR=japhet@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=464764
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=193158

[dcheng, 2015-04-04 13:36:21]

Created Revert of Refactor frame navigation/detach state cleanup to be more
sane.

[commit-bot: I haz the power, 2015-04-04 13:36:25]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1058403002/1

[commit-bot: I haz the power, 2015-04-04 13:37:19]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=193158