Make the ChromeBrowserInitializer the only way to start the browser process.
Removes the need for talking to the Android application,
which will allow us to slowly move browser specific class
initialization to something browser process specific.
BUG=
482445
Committed:
https://crrev.com/6c5bbb3ce0d88c89205776a553158c444c393c99
Cr-Commit-Position: refs/heads/master@{#364900}