Revert of Add switch (for cast_shell) to defer creation of GPU process.

Revert of Add switch (for cast_shell) to defer creation of GPU process. (patchset #8 id:140001 of https://codereview.chromium.org/1038783002/)

Reason for revert:
Breaking mac browser tests?

http://build.chromium.org/p/chromium.mac/builders/Mac10.6%20Tests/builds/436

BrowserGpuChannelHostFactoryTest.AlreadyEstablished (run #1):
[ RUN      ] BrowserGpuChannelHostFactoryTest.AlreadyEstablished
[35311:27139:0327/154011:20111614311426:ERROR:browser_gpu_channel_host_factory.cc(134)] Failed to launch GPU process.
[35311:27139:0327/154011:20111614504937:ERROR:browser_gpu_channel_host_factory.cc(134)] Failed to launch GPU process.
../../content/browser/gpu/gpu_ipc_browsertests.cc:179: Failure
Value of: event
  Actual: false
Expected: true
[  FAILED  ] BrowserGpuChannelHostFactoryTest.AlreadyEstablished, where TypeParam =  and GetParam() =  (215 ms)

Original issue's description:
> Add switch (for cast_shell) to defer creation of GPU process.
>
> For context - on Chromecast, we have the following scenario:
> * We support running in the background (i.e. not rendering anything)
>   with our service running in the browser process to listen for incoming
>   cast connections.
> * We cannot acquire any GPU resources (e.g. a GL context or surface)
>   during this time as another external application needs it, and it's a
>   global resource.
>
> We have supported starting up in the foreground and switching to this
> mode for a long time.
>
> But now, we need to support starting up in this mode.  In other words,
> we need to bring up the browser process and run our cast receiver
> service, but we cannot run any of the GPU process's initialisation
> code until an incoming cast arrives.
>
> BUG=internal b/19898960
>
> Committed: https://crrev.com/db7efe6dfbda08faa1e55cda4441b43dac005733
> Cr-Commit-Position: refs/heads/master@{#322655}

TBR=enne@chromium.org,nasko@chromium.org,piman@chromium.org,sievers@chromium.org,halliwell@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=internal b/19898960

Committed: https://crrev.com/6ab2e52d484e53a5bb25731b0463bb461992069f
Cr-Commit-Position: refs/heads/master@{#322668}

[danakj, 2015-03-27 22:57:00]

Created Revert of Add switch (for cast_shell) to defer creation of GPU process.

[commit-bot: I haz the power, 2015-03-27 22:57:23]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1043603002/1

[commit-bot: I haz the power, 2015-03-27 22:58:05]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-27 22:59:34]

Patchset 1 (id:??) landed as
https://crrev.com/6ab2e52d484e53a5bb25731b0463bb461992069f
Cr-Commit-Position: refs/heads/master@{#322668}