cc: Explicitly initialize member variables in test.
cc: Explicitly initialize member variables in test.

Dr Memory is complaining of uninintialized variable in
LayerTreeHostCopyRequestTestLostOutputSurface. I think the variable
must be used before it is read based on the flow control of the test,
also initializing to 0 and to 4 both pass. However, hopefully
explicit initialization will fix the analysis. There was no mention
of flakiness in the bug report.

R=enne
BUG=567439
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1505113003

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#363744}

axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk