Partially revert "Handle WebView assets correctly when multiple APKs are used."

This reverts the WebViewFactory changes from commit
527fa8f4 which appear to have changed
the way that the asset path is updated in an incompatible way.

Bug: 124116212
Fixes: 128489090
Test: launch affected applications
Change-Id: Id53dedef4fa55a6b8cea8a60326a4b8acd3422f8