[Android] Fix the regression issue of http authentication on chromium 34...

....

After rebased to chromium 34, the http authentication cannot work
as chromium 32, this is because Chromium 34 starts to support the
out-of-process iframe, RenderViewHost is replaced by RenderFrameHost,
while in XwalkLoginDelegate, webcontents is still got via the
RenderViewHost, which causes the corresponding UI thread for
http authentication not to work. This fix is resolving this issue
by replacing RenderView with RenderFrame for http authentication.

BUG=https://crosswalk-project.org/jira/browse/XWALK-1088