Cherry pick [Android WebView] Populate WebKit WebPreferences correctly in browser

Cherry pick of https://codereview.chromium.org/23619089/

Bug: 10911684

Orignal description:
Currently Android WebView will push settings from the java side to the
renderer, but if the browser needs to read those settings back we will
use a default set from WebContentsImpl as we neglect to override
ContentBrowserClient::OverrideWebKitPrefs. This means that the browser
and renderer can see out of sync preference values.

Change-Id: I432f6bbe5a57ae0cdc1596554900b21953909494
27 files changed