Add Client certificate support to AOSP browser

Bug: 14298085

The webview client cert API is not public at the time. This
change adds client certificate support to AOSP browser via this hidden
API mostly for testing purposes. We will be continuously updating Browser
as the API changes since browser is the main testing tool for it.

Change-Id: Idc993b4ebb5635a06435aaccdfa0e418a91ce48f
2 files changed