Disable GpuMetricsProvider if GPU is disabled.

Disable GpuMetricsProvider if GPU is disabled.

This was causing problems with some platforms in Aura's
CreateNativeScreen if GPU metrics were collected before Aura is
initialized.

Committed: https://crrev.com/f26779fd0b76f282d82bb33169c8c88dee8ba903
Cr-Commit-Position: refs/heads/master@{#304125}

[GusFernandez, 2014-11-13 22:11:35]

gusfernandez@chromium.org changed reviewers:
+ gunsch@chromium.org, lcwu@google.com

[lcwu1, 2014-11-13 22:14:58]

lcwu@chromium.org changed reviewers:
+ lcwu@chromium.org

[lcwu1, 2014-11-13 22:14:58]

lgtm

[GusFernandez, 2014-11-13 22:20:49]

The CQ bit was checked by gusfernandez@chromium.org

[commit-bot: I haz the power, 2014-11-13 22:22:10]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/721393002/1

[commit-bot: I haz the power, 2014-11-14 00:29:43]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-11-14 00:30:26]

Patchset 1 (id:??) landed as
https://crrev.com/f26779fd0b76f282d82bb33169c8c88dee8ba903
Cr-Commit-Position: refs/heads/master@{#304125}