Revert "Revert "Make dart_test generate a script to run the tests.""

The Flutter shell can now be successfully built on bots.

TO-341

This reverts commit 3b81183978b4e533aee3d2725fe3070b7fefc6cb.

Change-Id: If5dd2901e52613aa4b6e76fd8bf933796c1218a1
4 files changed