Fix incorrect extension check.
Fix incorrect extension check.

BUG=angleproject:884

Change-Id: Ia201ac60e337fd45ef72cc254bcb36d333418613
Reviewed-on: https://chromium-review.googlesource.com/289333
Reviewed-by: Geoff Lang <b6fc25fe0362055230985c05cbfa8adb741ccc0f@chromium.org>
Tested-by: Geoff Lang <b6fc25fe0362055230985c05cbfa8adb741ccc0f@chromium.org>

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