Revert of content: Cleanup GpuMemoryBuffers when child process is removed.

Revert of content: Cleanup GpuMemoryBuffers when child process is removed. (patchset #5 id:80001 of https://codereview.chromium.org/703463005/)

Reason for revert:
Blink layout tests are failing and this CL might be the cause. Let me revert this CL.

Original issue's description:
> content: Cleanup GpuMemoryBuffers when child process is removed.
>
> This keeps track of buffers allocated for child processes in
> BrowserGpuMemoryBufferManager and makes sure
> GpuMemoryBufferImpl::DeletedByChildProcess is called
> appropriately when a process is removed.
>
> BUG=
>
> Committed: https://crrev.com/32e22ea8b72f52ac89e5d5720d1a26596f015caf
> Cr-Commit-Position: refs/heads/master@{#302968}

TBR=piman@chromium.org,alexst@chromium.org,kenrb@chromium.org,reveman@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=

Committed: https://crrev.com/d1f3f55d090788dcb09321e6425fc953ac40ee0a
Cr-Commit-Position: refs/heads/master@{#302984}

[yhirano, 2014-11-06 08:24:02]

Created Revert of content: Cleanup GpuMemoryBuffers when child process is
removed.

[commit-bot: I haz the power, 2014-11-06 08:25:08]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/709433002/1

[commit-bot: I haz the power, 2014-11-06 08:26:02]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-11-06 08:26:42]

Patchset 1 (id:??) landed as
https://crrev.com/d1f3f55d090788dcb09321e6425fc953ac40ee0a
Cr-Commit-Position: refs/heads/master@{#302984}

[reveman, 2014-11-06 15:26:34]

On 2014/11/06 08:24:02, yhirano wrote:
> Created Revert of content: Cleanup GpuMemoryBuffers when child process is
> removed.

Did this revert fix the layout tests? In that case, what was the failure?

[yhirano, 2014-11-06 15:56:32]

On 2014/11/06 15:26:34, reveman wrote:
> On 2014/11/06 08:24:02, yhirano wrote:
> > Created Revert of content: Cleanup GpuMemoryBuffers when child process is
> > removed.
> 
> Did this revert fix the layout tests? In that case, what was the failure?

I pasted links to the original CL.