Update almost all tests (except co19) to use the new try-catch syntax.

tests/language/throw2_test.dart

Index: tests/language/throw2_test.dart
diff --git a/tests/language/throw2_test.dart b/tests/language/throw2_test.dart
index 7a9d20523e70ea5b80fdfb48f84c88fea2ef88f6..2b2c7dfde89a8e25c1520913ad88d883e370adbf 100644
--- a/tests/language/throw2_test.dart
+++ b/tests/language/throw2_test.dart
@@ -30,18 +30,18 @@ class Helper {
     try {
       int j;
       j = func();
-    } catch (MyException3 exception) {
+    } on MyException3 catch (exception) {
       i = 100;
       print(exception.getMessage());
-    } catch (MyException2 exception) {
+    } on MyException2 catch (exception) {
       try {
         i = func2();
         i = 200;
-      } catch (TestException exception) {
+      } on TestException catch (exception) {
         i = 50;
       }
       print(exception.getMessage());
-    } catch (MyException exception) {
+    } on MyException catch (exception) {
       i = func2();
       print(exception.getMessage());
     } finally {