Check for the extension before creating compressed textures in SwizzleTest.
Check for the extension before creating compressed textures in SwizzleTest.

Change-Id: Ia561fc7bb0262ab6974517d9796e4828db5b511c
Reviewed-on: https://chromium-review.googlesource.com/263251
Reviewed-by: Jamie Madill <7e492b4f1c8458024932de3ba475cbf015424c30@chromium.org>
Tested-by: Geoff Lang <b6fc25fe0362055230985c05cbfa8adb741ccc0f@chromium.org>

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