Revert of [DevTools] Remove edited scripts from debugger agent, move knowledge to frontend.

Revert of [DevTools] Remove edited scripts from debugger agent, move knowledge to frontend. (patchset #4 id:60001 of https://codereview.chromium.org/1238103002/)

Reason for revert:
I'm not sure it works the right way with the extensions / resources panel.

Original issue's description:
> [DevTools] Remove edited scripts from debugger agent, move knowledge to frontend.
> 
> Instead of requesting scripts through Page.getResourceContent, we should
> use Debugger.getScriptSource. NetworkProject does that.
> 
> A couple of race fixes along the way because of changed timings.
> 
> BUG=none
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=199161

TBR=yurys@chromium.org,sergeyv@chromium.org,dgozman@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=none

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=199174

[pfeldman, 2015-07-20 17:47:56]

Created Revert of [DevTools] Remove edited scripts from debugger agent, move
knowledge to frontend.

[commit-bot: I haz the power, 2015-07-20 17:48:07]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1240373002/1

[commit-bot: I haz the power, 2015-07-20 17:48:47]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=199174