[Android WebView] Put error page files into WebView resources
Historically, the load error pages displayed by WebView were a part of
Android framework resources. This change adds them into WebView
resources. This way, the pages will be accessible to sandboxed child
services, using Chromium's resource sharing mechanisms.
Unlike Chrome's error pages, which use WebUI, WebView pages are
completely static, as JavaScript can be disabled.
BUG=515691
Review URL: https://codereview.chromium.org/
1270793002
Cr-Commit-Position: refs/heads/master@{#341951}