Fix JSON encoder accepting NaN and Infinity.

tests/lib/convert/json_test.dart

Index: tests/lib/convert/json_test.dart
diff --git a/tests/corelib/json_test.dart b/tests/lib/convert/json_test.dart
similarity index 97%
rename from tests/corelib/json_test.dart
rename to tests/lib/convert/json_test.dart
index 86485e02404e8bc02562a92746fdecfd2a0f874f..4470535578aced1a25d1298013c4a70609ffd69d 100644
--- a/tests/corelib/json_test.dart
+++ b/tests/lib/convert/json_test.dart
@@ -135,6 +135,13 @@ testNumbers() {
 
   testThrows("[2.,2]");
   testThrows("{2.:2}");
+
+  testThrows("NaN");
+  testThrows("Infinity");
+  testThrows("-Infinity");
+  Expect.throws(() => JSON.encode(double.NAN));
+  Expect.throws(() => JSON.encode(double.INFINITY));
+  Expect.throws(() => JSON.encode(double.NEGATIVE_INFINITY));
 }
 
 testStrings() {