Revert of Fixes document type detection on iOS 9.

Revert of Fixes document type detection on iOS 9. (patchset #1 id:1 of https://codereview.chromium.org/1491043004/ )

Reason for revert:
No approval for this cherry-pick. Reverting.

Original issue's description:
> Fixes document type detection on iOS 9.
> 
> On iOS 9, evaluating '' + document always results in [object
> HTMLDocument], even for PDFs. This introduces another way of checking
> document type on iOS 9. Unfortunately, it doesn't work on iOS 8, so the
> old implementation needs to stay too.
> 
> BUG=549604
> 
> Review URL: https://codereview.chromium.org/1458703004
> 
> Cr-Commit-Position: refs/heads/master@{#361095}
> (cherry picked from commit 704def3b29d00bf39aca6553a079152171af4ad9)
> 
> Committed: https://chromium.googlesource.com/chromium/src/+/f5f194b3efbdfc92886eebe0b359a25518061fe0

TBR=
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=549604

[bzanotti, 2015-12-02 16:43:34]

Created Revert of Fixes document type detection on iOS 9.

[commit-bot: I haz the power, 2015-12-02 16:43:55]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1491263002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1491263002/1

[commit-bot: I haz the power, 2015-12-02 16:45:31]

Committed patchset #1 (id:1)