Bug 750901 - Elm to mc migration work - metro related changes to Windows widget src to support building metro winrt bits (nsWidgetFactory, nsWindowGfx, nsToolkit, WinUtils). Also landing nsIWinMetroUtils.idl. r=bbondy

widget/windows/WinTaskbar.cpp

@@ -240,6 +240,11 @@ WinTaskbar::~WinTaskbar() {
 // static
 bool
 WinTaskbar::GetAppUserModelID(nsAString & aDefaultGroupId) {
+  // For win8 metro builds, we can't set this. The value is static
+  // for the app.
+  if (XRE_GetWindowsEnvironment() == WindowsEnvironmentType_Metro) {
+    return false;
+  }
   // If marked as such in prefs, use a hash of the profile path for the id
   // instead of the install path hash setup by the installer.
   bool useProfile =