Javacrash java.lang.NullPointerException in com.android.browser.

Provide a WebView interface in WebSettings, for BrowserSettings need to access it.

Change-Id: I8a4b9c9a746c9c0b2a1a6adec35943de9fb2f9b0
Author: Yijun Zhu <yijunx.zhu@intel.com>
Signed-off-by: Yijun Zhu <yijunx.zhu@intel.com>
Signed-off-by: Shuo Gao <shuo.gao@intel.com>
Signed-off-by: Bruce Beare <bruce.j.beare@intel.com>
Signed-off-by: Jack Ren <jack.ren@intel.com>
Author-tracking-BZ: 34962