Revert of Enable Oilpan by default for websockets/ (https://codereview.chromium.org/429293003/)

Reason for revert:
Causes crashes in websocket browser tests

e.g. http://build.chromium.org/p/chromium.webkit/builders/Linux%20ChromiumOS%20Tests%20%28dbg%29%281%29/builds/533/steps/browser_tests/logs/stdio

Bisected locally to find this revision.

Original issue's description:
> Enable Oilpan by default for websockets/
> 
> This CL basically just drops WillBe types from websocket objects. Non-trivial parts are:
> 
> - Changed MockWebSocketChannelClient from RefCountedGarbageCollected to GarbageCollectedFinalized since it doesn't need to be RefCounted.
> 
> - Marked AllowCrossThreadAccessWrapper as STACK_ALLOCATED, and intentionally allowed to use a raw pointer to T*. Ideally this should be Member<T> if T inherits from GarbageCollected, but I don't want to introduce another template magic just to distinguish Member<T> from T* on stack-allocated objects. Added a comment about it.
> 
> BUG=340522
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=179336

TBR=oilpan-reviews@chromium.org,tyoshino@chromium.org,yhirano@chromium.org,ricea@chromium.org,tkent@chromium.org,haraken@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=340522

Review URL: https://codereview.chromium.org/429453008

git-svn-id: svn://svn.chromium.org/blink/trunk@179351 bbb929c8-8fbe-4397-9dbb-9b2b20218538