API level 19 means Android 4.4 KitKat, in which the browser engine is switched from Android webkit to chromium webkit, with almost all the original WebView APIs wrapped to the counterparts of chromium webkit.
That means most of the implementations of WebView APIs are different from Android 4.3 and before, incuding the database storage API. That also means since Android 4.4 developers cannot (or don't have to) assign an alternative db path; all this is handled by Android by default.
managed by the implementation
now means the database storage path is handled by chromium webkit engine by default, while before Android 4.4 it's handled in android.webkit
in framework layer which needs to be set.