Allow switching to the Chromium WebViewFactoryProvider at runtime.

Currently, WebViewFactory is hardcoded to always load
android.webkit.WebViewClassic$Factory.  This change allows us to
load the Chromium powered WebView by setting the
"webview.use_chromium" system propery to true.

Change-Id: Icebfc4d5c4a61230c5e5dccac1ec5eca59f650ac
1 file changed