Shell instances launched by the tools from the desktop are always non-interactive. (#5778)

In that they never create a window with an OpenGL context and the works.

bin/cache/engine.version

-d3ba01d8a48b96829957e1c1a28a6034974f79ae
+a55fa1efb90b83c56004f12ee67673f4836eb33d

packages/flutter_tools/lib/src/test/flutter_platform.dart

@@ -61,9 +61,10 @@ Future<Process> _startProcess(String mainPath, { String packages, int observator
   if (observatoryPort != null) {
     arguments.add('--observatory-port=$observatoryPort');
   } else {
-    arguments.add('--non-interactive');
+    arguments.add('--disable-observatory');
   }
   arguments.addAll(<String>[
+    '--non-interactive',
     '--enable-checked-mode',
     '--packages=$packages',
     mainPath