Enable multiprocess WebView by default.

Make the multiprocess WebView enabled by default. It can be disabled by
the user in developer settings, but will be re-enabled after the WebView
implementation is updated to keep people testing it.

Bug: 21643067
Test: verify that WebView is enabled by default in developer settings
Change-Id: I100dac6b4d3784678a694352faa6e9fb2fc72078
1 file changed