Add a new app API to enable watchdog behavior restarts in kiosk apps

This CL adds chrome.runtime.restartAfterDelay(int seconds, callback) to enable
watchdog behavior restarts in kiosk apps.

BUG=604578
TEST=browser_tests --gtest_filter=RestartAfterDelayApiTest.RestartAfterDelayTest

Review-Url: https://codereview.chromium.org/1970613003
Cr-Commit-Position: refs/heads/master@{#400027}
10 files changed