Example URL:
https://reverb.com/

Steps to reproduce the problem:
1. Create project with android:targetSdkVersion="18" (or lower) in Android manifest
2. Create WebView with JavaScript, wide viewport, and open in overview all enabled
3. Load https://reverb.com/ in WebView
4. Once site loads, tap the 3 bar "hamburger" menu button in the upper right corner of the site

What is the expected behavior?
The 3 bar "hamburger" menu button should open the site menu.

What went wrong?
When SDK target is set to 18 or lower in the Android manifest, the site's menu will not work. When the SDK target is set to 19 or higher, the menu button will open the menu.

This is just one example. I suspect that the target set <= 18 is responsible for strange site behavior and rendering on other sites too.

Also reported this in the Android bug DB a while back:
https://code.google.com/p/android/issues/detail?id=82880

Does it occur on multiple sites: Yes

Is it a problem with a plugin? No 

Did this work before? Yes pre-Chromium WebView before Android 4.4

Does this work in other browsers? Yes 

Chrome version: 52.0.2743.32  Channel: n/a
OS Version: 6.0.1
Flash Version: none