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

tests/language/arithmetic_test.dart

Index: tests/language/arithmetic_test.dart
diff --git a/tests/language/arithmetic_test.dart b/tests/language/arithmetic_test.dart
index fef30b8b6e75a441c16c1b0fcc203958d3148c10..f2224f6280993d455a6df3f5556dc4a600c9d643 100644
--- a/tests/language/arithmetic_test.dart
+++ b/tests/language/arithmetic_test.dart
@@ -12,7 +12,7 @@ class ArithmeticTest {
     try {
       parseInt(s);
       return false;
-    } catch (FormatException e) {
+    } on FormatException catch (e) {
       return true;
     }
   }
@@ -21,7 +21,7 @@ class ArithmeticTest {
     try {
       parseDouble(s);
       return false;
-    } catch (FormatException e) {
+    } on FormatException catch (e) {
       return true;
     }
   }
@@ -32,7 +32,7 @@ class ArithmeticTest {
     try {
       var a = d.toInt();
       return false;
-    } catch (FormatException e) {
+    } on FormatException catch (e) {
       return true;
     }
   }