Phase-2 API takes a hostname

For phase-2, instead of taking a hash prefix, we will send the
hostname to the resolver.

Bug: 25119046
Test: build & install the sample resolver and run 'adb shell am start -a android.intent.action.VIEW -c android.intent.category.BROWSABLE -d "https://www.tripadvisor.com/Tourism-g33020-San_Jose_California-Vacations.html"'
Change-Id: I6e621139e182f9a9cfcf608c26d4763f1379bdb2