Expose isMultiProcessEnabled via WebViewDelegate.

Allow the WebView implementation to call isMultiProcessEnabled via the
delegate, so that it doesn't have to fetch and interpret the value of
the system setting itself.

Bug: 21643067
Test: manual (requires modifications to chromium to call)
Change-Id: I1ef2b7ea0054c606965040e02034c938d5e6464c
2 files changed