QWebView widget missing from Display Widgets in Qt Creator

I have Qt Creator and Qt4 Designer installed on Ubuntu 12.04, and they seem to work fine.
I recently installed these same two packages on a different computer running Ubuntu 14.04.
and the QWebView widget was missing from the Display Widgets rubric.
I searched for solutions to the problem and found one proposed solution: simply copy the file
"libqwebview.so" into the directory
/usr/lib/x86_64-linux-gnu/qt4/plugins/designer
I did that, and after that the QWebView widget did display in Qt4 Designer. However, it still
doesn't display in Qt Creator. Also, on my computer on which the QWebView icon appears
normally I find only one instance of this file. This suggests that there is a different problem
with Qt Creator: either the plugin has a different name or it uses the Qt4 Designer plugins
but keeps a list of the widgets to display and the list no longer matches the ones that are
actually present in that directory.
Does anyone have any idea how to get the QWebView icon to appear normally in
Qt Creator? I've tried uninstalling and reinstlaling both programs many times.
Thanks in advance for any suggestions.
Tom