Device name: Nexus 5
Android version: 5.0
WebView version (from system settings -> Apps -> Android System WebView):
55.0.2883.45
Application:
Opera mini
https://play.google.com/store/apps/details?id=com.opera.mini.native
or
Yahoo! Browser
https://play.google.com/store/apps/details?id=jp.co.yahoo.android.ybrowser

Application version:
Opera mini 20.0.2254.109835
Yahoo! Browser 2.0.20


URLs (if applicable):
http://www.w3schools.com/html/html_forms.asp


Steps to reproduce:
(1) Open URL
(2) Type "test" in "First name:"
(3) Tap "Submit"
(4) Press back key
(5) Again, type "test"

Expected result:
Saved string ("test") is displayed

Actual result:
Nothing happens