browser: allow to load browser internal assets

The new webview classes avoid to load urls from local file schemes. Just replace the load of internal browser assets (most_visited) from loadUrl to loadData.

Change-Id: Iee633a1a3599a7e752e15452fa04e15baac2e256
JIRA: CYAN-3564
Issue: https://jira.cyanogenmod.org/browse/CYAN-3564
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>