Rovert asks: “What is RTLMirroring?

The answer comes from Marin who is responsible for Visual Studio Localization:

We made a breaking change to the RTL behavior for controls inheriting from the common control, so we added this new method in case someone needed to disable the new behavior for backward compatibility.  However, we believe that most users in Whidbey will want the new behavior by default, so that’s why we need this in the template file.