Add infrastructure to run tests on android.

mojo/edk/test/multiprocess_test_helper.h

Index: mojo/edk/test/multiprocess_test_helper.h
diff --git a/mojo/edk/test/multiprocess_test_helper.h b/mojo/edk/test/multiprocess_test_helper.h
index d131460228aaf69494c9fa3ed23b67cd24a11392..265c1730cfbd0d21e3cd3a4aa68a7fff928c942d 100644
--- a/mojo/edk/test/multiprocess_test_helper.h
+++ b/mojo/edk/test/multiprocess_test_helper.h
@@ -14,6 +14,13 @@
 #include "mojo/edk/embedder/scoped_platform_handle.h"
 #include "testing/multiprocess_func_list.h"
 
+// Multi process tests are not supported on android, because the platform
+// doesn't provide an executable to exec and only forking is too hacky and
+// fragile.
+#if defined(OS_ANDROID)
+#error "Multi process tests are not supported."
+#endif
+
 namespace mojo {
 
 namespace embedder {