Update Chromium HTTP stack to get database and cache paths from CookieSyncManager

Currently these paths are obtained from the BrowserFrame via JNI.
However, the paths are not synced to the BrowserFrame until the
WebCore thread has started up. This means that if the
WebRequestContext is created on the IO thread, the paths may not be
available.

This change moves the paths from BrowserFrame to CookieSyncManager to
avoid the need to wait for the WebCore thread.

Note that the new methods may be called on either the UI or WebCore
threads, so are synchronised.

Requires a change to external/webkit ...
https://android-git.corp.google.com/g/76579

Change-Id: I8e910ee209c570e90181bd308a78d1987b4d120c