It emits spurious -Wmaybe-uninitialized warnings. Initializing these variables
shouldn't do any harm (with an optimizing compiler), so this seems the quickest
way to mollify gcc.

BUG=chromium:148757

Review-Url: https://codereview.chromium.org/2290653003
Cr-Commit-Position: refs/heads/master@{#39000}