Fix test flakiness: http/tests/inspector/command-line-api-inspect.html

BUG=307294
R=pfeldman

Review URL: https://codereview.chromium.org/100613003

git-svn-id: svn://svn.chromium.org/blink/trunk@163085 bbb929c8-8fbe-4397-9dbb-9b2b20218538