Revert 269361 "Fix WebURLLoaderImpl::Context leak if a pending r..."

Revert 269361 "Fix WebURLLoaderImpl::Context leak if a pending r..."

This is currently causing a top crasher; tfarina@ rebuilt on a branch
without this patch and have confirmed that reverting it fixes the crash.

Reverting at the request of the TPMs.

> Fix WebURLLoaderImpl::Context leak if a pending request is canceled.
> 
> Now, ResourceDispatcher::CancelPendingRequest will send
> ResourceHostMsg_CancelRequest and trigger OnRequestComplete. However,
> the request is pending and thus OnRequestComplete will be queued.
> 
> There are at least two problems if OnRequestComplete is not called:
> 1. WebURLLoaderImpl::Context will never be released.
> 2. request_info->buffer leaks. The buffer holds shared memory handle
>    (file descriptor). fd leaking may lead to HW video decode failure on
>    ChromeOS (detail in chrome-os-partner:27911#63)
> 
> This issue is similar to issue 328092.
> 
> BUG=chrome-os-partner:27911, chromium:369221, chromium:369128
> R=jam@chromium.org, mmenke@chromium.org
> 
> Review URL: https://codereview.chromium.org/268423002

BUG=372342
TBR=kcwu@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=271504

[Elliot Glaysher, 2014-05-19 22:34:42]

Committed patchset #1 manually as r271504 (tree was closed).