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

tests/language/throw4_test.dart

Index: tests/language/throw4_test.dart
diff --git a/tests/language/throw4_test.dart b/tests/language/throw4_test.dart
index 66e831900f80b113c020adb7a363adbd3aef851a..6b4a36d12d10b1ec3fe0c42abb370bfbf3de4f09 100644
--- a/tests/language/throw4_test.dart
+++ b/tests/language/throw4_test.dart
@@ -25,13 +25,13 @@ class Helper {
     int j = 0;
     try {
       j = func();
-    } catch (MyException3 exception) {
+    } on MyException3 catch (exception) {
       i = i + 300;
       print(exception.message_);
-    } catch (MyException2 exception) {
+    } on MyException2 catch (exception) {
       i = i + 200;
       print(exception.message_);
-    } catch (MyException1 exception) {
+    } on MyException1 catch (exception) {
       i = i + 100;
       print(exception.message_);
     } finally {
@@ -52,10 +52,10 @@ class Helper {
       if (i > 0) {
         throw new MyException1("Test for MyException1 being thrown");
       }
-    } catch (MyException3 exception) {
+    } on MyException3 catch (exception) {
       i = 300;
       print(exception.message_);
-    } catch (MyException2 exception) {
+    } on MyException2 catch (exception) {
       i = 200;
       print(exception.message_);
     } finally {