[vr] Don't draw the reticle at the origin

Previously, we would return the identity transform in this case causing
flashes.

Bug: None
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_vr;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: I220235f11e9eccab025a97e549bfa1dfca9843b1
Reviewed-on: https://chromium-review.googlesource.com/1007002
Reviewed-by: Christopher Grant <cjgrant@chromium.org>
Commit-Queue: Ian Vollick <vollick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#549940}
2 files changed