Add an API to enable disable safebrowsing in WebView

WebView safebrowsing can be opted in using a manifest value. However,
we also need to control individual WebViews.

Bug:37158813
Test: See change I71e813bccc2fab73d100384661128c7311dd396c

Change-Id: I647dc304787d6406691b5cbadf1c9a4f13ac5604
4 files changed