Revert of Add a NavigationThrottle to the public content/ interface

Revert of Add a NavigationThrottle to the public content/ interface (patchset #18 id:350001 of https://codereview.chromium.org/1269813002/ )

Reason for revert:
linux_chromiium_chromeos_rel_ng => browser_test => SelectFileDialogExtensionBrowserTest seems to faile a lot, testing.

Original issue's description:
> Add a NavigationThrottle to the public content/ interface
>
> This CL adds a NavigationThrottle class to the public content/ interface. A NavigationThrottle is used to control the flow of navigations. It lives entirely on the UI thread. Eventually, all components that want the functionality of a ResourceThrottle for navigations should transition to a NavigationThrottle: the new architecture for navigations (browser-side navigation) will not support ResourceThrottles for main resources load. See https://docs.google.com/document/d/1ICLLQoC9EsZ-bWH4ZKRhPCIoZKn6pOj02SlGl6SKH6Y/edit?pli=1#heading=h.fmxjmgvbgg7x for the design doc.
>
> This Cl also transition the InterceptNavigationresourceThrottle to the Navigationthrottle model.
> BUG=504347
>
> Committed: https://crrev.com/394057986ff5d00a841a976f3bd8d599603acaa1
> Cr-Commit-Position: refs/heads/master@{#350092}

TBR=nasko@chromium.org,davidben@chromium.org,carlosk@chromium.org,fdegans@chromium.org,avi@chromium.org,creis@chromium.org,nick@chromium.org,asargent@chromium.org,sky@chromium.org,mnaganov@chromium.org,clamy@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=504347
Committed: https://crrev.com/2ad8595f7a925851acd3ae733f359fafe6223ff5
Cr-Commit-Position: refs/heads/master@{#350157}

[huangs, 2015-09-22 14:49:22]

Created Revert of Add a NavigationThrottle to the public content/ interface

[huangs, 2015-09-22 15:29:21]

The CQ bit was checked by huangs@chromium.org

[commit-bot: I haz the power, 2015-09-22 15:29:59]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1350913008/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1350913008/1

[commit-bot: I haz the power, 2015-09-22 15:31:27]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-09-22 15:31:59]

Patchset 1 (id:??) landed as
https://crrev.com/2ad8595f7a925851acd3ae733f359fafe6223ff5
Cr-Commit-Position: refs/heads/master@{#350157}

[huangs, 2015-09-22 16:37:06]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/1357803004/ by huangs@chromium.org.

The reason for reverting is: Test failure on linux_chromium_chromeos_rel_ng is
fixed, but to be sure (e.g., it's not a problem with test bot?) let's see if bug
reappears when we undo the revert..

[huangs, 2015-09-22 18:05:27]

*Not* relanding: Result of https://codereview.chromium.org/1357803004/ verifies
that relanding would lead to test failure.