Clang warns if there are missing braces around a subobject
initializer. The most common idiom that triggers this is:
  STRUCT s = {0};
if the first field of STRUCT is itself a struct. This can
be more simply written as:
  STRUCT s = {};
which also prevents the warning from firing.

BUG=chromium:505297
LOG=n

Review URL: https://codereview.chromium.org/1219233003

Cr-Commit-Position: refs/heads/master@{#29437}