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

tests/language/throw7_negative_test.dart

Index: tests/language/throw7_negative_test.dart
diff --git a/tests/language/throw7_negative_test.dart b/tests/language/throw7_negative_test.dart
index 69879af63b35f35322a29ea1e34c42937857461c..7ab33b6ec80d1521a879ed209cc9fa2344b624f3 100644
--- a/tests/language/throw7_negative_test.dart
+++ b/tests/language/throw7_negative_test.dart
@@ -15,13 +15,13 @@ class Helper {
     int j = 0;
     try {
       j = i;
-    } catch (var exception) {
+    } catch (exception) {
       i = i + 100;
       print(exception.message_);
     }
     // Since there is a generic 'catch all' statement preceding this
     // we expect to get a dead code error/warning over here.
-    catch (MyException1 exception) {
+    on MyException1 catch (exception) {
       i = i + 100;
       print(exception.message_);
     }