callback/callback-android — comment on commit c70a1e8594582a67a795bdef347f9f80c7553574
File:  line 0
By macdonst:

Near the top of that page it says:

By default, WebView scales a web page so that it is drawn at a size that matches the default appearance on a medium density screen. So, it applies 1.5x scaling on a high density screen (because its pixels are smaller) and 0.75x scaling on a low density screen (because its pixels are bigger). Starting with API Level 5 (Android 2.0), WebView supports DOM, CSS, and meta tag features to help you (as a web developer) target screens with different screen densities.

It's under the section "Building web pages to support different screen densities". If it breaks the meta viewport tag. Which it doesn't appear to do as you can over-ride this setting by using the "target-densitydpi" property we can revert it. Mind you I didn't test every last version of Android for bugs.