Hi @sgiehl - thanks for the PR!
looks good to me. @tsteur maybe you have some opinion as well?

I'm not sure re the name isDefaultTypeFixed. In the context of Report I would not think of a fixed ViewDataTable/Visualization.

Would maybe also rather check for isFixed... in https://github.com/piwik/piwik/blob/2.10.0/core/ViewDataTable/Factory.php#L92 instead of in report class then it works everywhere as ViewDataTabe::build is also called in other places. We are getting the report eg here: https://github.com/piwik/piwik/blob/2.10.0/core/ViewDataTable/Factory.php#L161

@tsteur better that way?

Sorry can you maybe rename isDefaultTypeFixed to something like alwaysUseDefaultViewDataTable or isViewDataTableFixed or maybe you have a better idea? I know it is not much better but a bit more consistent with getDefaultTypeViewDataTable for plugin developers. Not sure why I named it getDefaultTypeViewDataTable initially, not such a great name...

Side note: Would be nice to use for Piwik 3.0 the wording Visualization instead of ViewDataTable even if it is technically wrong (as the base class is currently called ViewDataTable which we would have to rename) but much more clearer for everyone what is meant.

@tsteur changed method name to alwaysUseDefaultViewDataTable. If everything is fine now, feel free to merge.