Fix for 10530176 - CookieSyncManager must be created by WebView c'tor

WebViewClassic created the CookieSyncManager instane as a side effect of
starting up its internal WebCoreThread. As this forms part of th API
contract (app doesn't need to call CookieSyncManager.createInstance if
it already made a WebView instance) promote this logic up to the API
layer.

Change-Id: I0e92d97be987dfef90162ad379c79b066aae34e0