[Android WebView] Make web contents debugging controllable

This change introduces a controller Java class AwDevToolsServer
for dynamically controlling the state of web debugging.
This change also removes the temporary remote debugging landing
page, as chrome://inspect now fully supports WebView.

BUG: 8691809

Upstream trunk patch: http://crrev.com/24238007

Change-Id: I9315272f39e59978bb723458706c8ec56498dbf1
10 files changed