[chromedriver] Handle Tracing.end response for Chrome 40 and earlier builds

BUG=chromedriver:997
TBR=stgao@chromium.org

Review URL: https://codereview.chromium.org/791613003

Cr-Commit-Position: refs/heads/master@{#307663}
Update chromedriver to use the new version of LaunchProcess.

BUG=417532

Review URL: https://codereview.chromium.org/793453002

Cr-Commit-Position: refs/heads/master@{#307999}