Fix static warnings in test_suite.dart from local variables shadowing parameters or functions.

client/tests/dartc/test_config.dart

Index: client/tests/dartc/test_config.dart
diff --git a/client/tests/dartc/test_config.dart b/client/tests/dartc/test_config.dart
index 180ca03511c5d5d3658cb62b563dd5343eca5e20..ba19cc76fe9c133b5496b24cba0750e8d8014364 100644
--- a/client/tests/dartc/test_config.dart
+++ b/client/tests/dartc/test_config.dart
@@ -29,8 +29,10 @@ class ClientDartcTestSuite extends DartcCompilationTestSuite {
 
   bool isTestFile(String filename) {
     if (!filename.endsWith(".dart")) return false;
-    var options = optionsFromFile(filename);
-    return optionsFromFile(filename)["containsLeadingHash"];
+    // Using readOptionsFromFile here causes the file to be read twice,
+    // because readOptionsFromFile is called again in the superclass.
+    // Avoid this in new code.
+    return readOptionsFromFile(filename)["containsLeadingHash"];
   }
 
   bool listRecursively() => true;