Revert of Refactor Script(Loader|Runner): don't access Resources all over the place...

Revert of Refactor Script(Loader|Runner): don't access Resources all over the place... (patchset #5 id:80001 of https://codereview.chromium.org/656113002/)

Reason for revert:
Introduced leaks in the following tests:

fast/dom/HTMLScriptElement/append-child-adopt-node-error-crash.html
fast/dom/HTMLScriptElement/script-async-attr.html
fast/dom/HTMLScriptElement/script-load-events.html
fast/dom/URL-attribute-reflection.html
fast/events/onerror-bubbling.html
http/tests/cache/loaded-from-cache-after-reload.html
http/tests/cache/subresource-expiration-2.html
http/tests/cache/subresource-multiple-instances.html
http/tests/htmlimports/import-script-block-crossorigin-dynamic.html
http/tests/loading/script-priorities.html

Original issue's description:
> Refactor Script(Loader|Runner): don't access Resources all over the place...
> 
> ... but use proper layering instead.
> 
> PendingScript holds a Resource, and many places in the code are using both the
> PendingScript and the underlying Resource. For example, ScriptRunner holds a
> collection of PendingScripts, and ScriptLoaders then listen to the underlying
> Resources. This is confusing and error prone.
> 
> The Resource - ScriptLoader - PendingScript - Element love quadrangle is messy
> in general.  Both ScriptLoader and PendingScript refer to the Resource. The way
> to get ScriptLoader from PendingScript is via Element which PendingScript also
> holds. But there's no way to get PendingScript from ScriptLoader.
> 
> This CL makes ScriptRunner access the ScriptLoaders directly and moves the
> PendingScript to ScriptLoader. In addition, it makes ScriptRunner not access the
> Resource of the ScriptLoader directly.
> 
> This CL also cancels the hack from https://bugs.webkit.org/show_bug.cgi?id=92211
> (r139942) where it was speculated that a crash can be caused by ScriptLoader
> getting the notifyFinished notification twice because it doesn't unsubscribe yet
> when it gets the first one. The speculative fix was to made it nullify
> ScriptLoader::m_resource and check for the nullity later. This is pretty
> surprising, since the obvious solution would've been to just unsubscribe early
> enough (which is done by this CL).
> 
> Note a behavioral change: It's OK to call Resource::addClient even if the
> Resource is finished, and in that case, the client will be notified
> immediately. But PendingScript used to ASSERT that the Resource is not
> finished. This CL removes that restriction (the underlying Resource already
> handles adding clients to finished resources + made ScriptStreamer handle it
> too).
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=183873

TBR=jochen@chromium.org,haraken@chromium.org,morrita@chromium.org,sigbjornf@opera.com,marja@chromium.org
NOTREECHECKS=true
NOTRY=true

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=183952

[dstockwell, 2014-10-19 23:19:16]

Created Revert of Refactor Script(Loader|Runner): don't access Resources all
over the place...

[commit-bot: I haz the power, 2014-10-19 23:19:45]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/669503003/1

[commit-bot: I haz the power, 2014-10-19 23:20:35]

Committed patchset #1 (id:1) as 183952

[haraken, 2014-10-19 23:32:14]

LGTM