Disable MRT support when using D3D10 feature levels.
Disable MRT support when using D3D10 feature levels.

D3D10 cards perform poorly when the pixel shader outputs to multiple
render targets that are not bound.

BUG=325581

Change-Id: I13f6f98861ffeb77cd21f7401ded4425e4ea7841
Reviewed-on: https://chromium-review.googlesource.com/185400
Reviewed-by: Shannon Woods <0f3694938fd5703bd548127ee497e4d604509bef@chromium.org>
Tested-by: Geoff Lang <b6fc25fe0362055230985c05cbfa8adb741ccc0f@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/190341

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