Revert of Don't refer browser-initiated navigations to web-safe URLs to delegate.

Revert of Don't refer browser-initiated navigations to web-safe URLs to delegate. (patchset #2 id:20001 of https://codereview.chromium.org/1234403005/ )

Reason for revert:
Since this CL was landed something has changed that causes clinking on links in the PDF viewer (embedded inside another WebView, e.g. the Chrome app "Browser Sample") to open in the wrong window, or in the case of "Open in a new tab", not be opened at all.

Reverting this CL fixes
https://code.google.com/p/chromium/issues/detail?id=529187 and
https://code.google.com/p/chromium/issues/detail?id=521573

A new bug has been filed to capture the error where the links are not opened in the correct target window:

https://code.google.com/p/chromium/issues/detail?id=532621

Original issue's description:
> Don't refer browser-initiated navigations to web-safe URLs to delegate.
>
> In a previous CL (https://codereview.chromium.org/890183002) it was
> decided to refer browser-initiated navigations to the owner WebContents'
> delegate, on the assumption that the navigation was to a non-web-safe
> url (e.g. a "chrome"-scheme url). However, this change can block
> guest navigations to web-safe URLs just because they originated, for
> example, from an extension.
>
> This CL ensures that navigations to web-safe URLs are not referred to
> the delegate in order to allow them to succeed.
>
> BUG=488053
>
> Committed: https://crrev.com/a03c23d32d176daf1e95cfffbfa333316e1eb1a6
> Cr-Commit-Position: refs/heads/master@{#339204}

TBR=creis@chromium.org,lazyboy@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=488053
Committed: https://crrev.com/b7d53cf36c29e13532afa89aa09fd89e8e1c8e95
Cr-Commit-Position: refs/heads/master@{#349208}

[wjmaclean, 2015-09-16 20:15:47]

Created Revert of Don't refer browser-initiated navigations to web-safe URLs to
delegate.

[commit-bot: I haz the power, 2015-09-16 20:16:40]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1350893002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1350893002/1

[commit-bot: I haz the power, 2015-09-16 20:18:40]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-09-16 20:20:10]

Patchset 1 (id:??) landed as
https://crrev.com/b7d53cf36c29e13532afa89aa09fd89e8e1c8e95
Cr-Commit-Position: refs/heads/master@{#349208}

[commit-bot: I haz the power, 2015-09-23 13:00:02]

Patchset 1 (id:??) landed as
https://crrev.com/b7d53cf36c29e13532afa89aa09fd89e8e1c8e95
Cr-Commit-Position: refs/heads/master@{#349208}