Register a default instance of FeatureList for content browser.
Normally, this is done in chrome_browser_main.cc in Chrome, but
given that we can't expect the embedder to necessarily initialize
the FeatureList, provide a default one if the embedder didn't.
This fixes an error when running Content Shell encountered by CLs
starting to use FeatureList, which didn't initialize the FeatureList
prior to this CL.
BUG=548289
Review URL: https://codereview.chromium.org/1409933007
Cr-Commit-Position: refs/heads/master@{#357437}
3 files changed
