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

tests/language/exception_test.dart

Index: tests/language/exception_test.dart
diff --git a/tests/language/exception_test.dart b/tests/language/exception_test.dart
index e0bae3b9fa088c433e024f080512c887ef7de857..c08a872556ce0cb481595844442db42588df4119 100644
--- a/tests/language/exception_test.dart
+++ b/tests/language/exception_test.dart
@@ -6,14 +6,14 @@ class ExceptionTest {
     int i = 0;
     try {
       throw "Hello";
-    } catch (String s) {
+    } on String catch (s) {
       print(s);
       i += 10;
     }
 
     try {
       throw "bye";
-    } catch (String s) {
+    } on String catch (s) {
       print(s);
       i += 10;
     }
@@ -23,11 +23,11 @@ class ExceptionTest {
     try {
       // This throws NullPointerException.
       throw null;
-    } catch (String s) {
+    } on String catch (s) {
       correctCatch = false;
-    } catch (NullPointerException e) {
+    } on NullPointerException catch (e) {
       correctCatch = true;
-    } catch (var x) {
+    } catch (x) {
       correctCatch = false;
     }
     Expect.isTrue(correctCatch);