Pass --minify to dart2dart if --minified was specified on test.py

Currently --minified on test.py has only an effect on dart2js commands.
The dart2dart commands use the legacy --additional-compiler-flags="--minify"
option.

This change is the first one of two CLs, where we pass --minify to dart2dart
if --minified was specified on test.py.

The second change will then remove the --additional-compiler-flags option
as soon as the build bots have been updated to use the new scheme for dart2dart.

Review URL: https://codereview.chromium.org//11419089

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@15144 260f80e4-7a28-3924-810f-c04153c831b5

tools/testing/dart/test_suite.dart

@@ -1587,9 +1587,8 @@ class TestUtils {
         args.add("--allow-mock-compilation");
       }
     }
-    // TODO(riocw): Unify our minification calling convention between dart2js
-    // and dart2dart.
-    if (compiler == "dart2js" && configuration["minified"]) {
+    if ((compiler == "dart2js" || compiler == "dart2dart") &&
+        configuration["minified"]) {
       args.add("--minify");
     }
     return args;