Cleanup to Resource11's reset method. Only reset when the resource is valid. This will prevent a memory allocation that could happen when triggering suprious reset() calls. BUG=angleproject:1155 Change-Id: I3b9bc1f9e0542c14ed5fd4a03f82ad23c94b734b Reviewed-on: https://chromium-review.googlesource.com/659231 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org>