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

tests/language/math_vm_test.dart

Index: tests/language/math_vm_test.dart
diff --git a/tests/language/math_vm_test.dart b/tests/language/math_vm_test.dart
index afc975caf3227c50c2d0620da9423b0bfef5776a..e8314f5c9369d7bb48ce73c34925eec67d2bf3da 100644
--- a/tests/language/math_vm_test.dart
+++ b/tests/language/math_vm_test.dart
@@ -18,7 +18,7 @@ class MathTest {
     try {
       parseInt(x);  // Expects string.
       return true;
-    } catch (var e) {
+    } catch (e) {
       return false;
     }
   }
@@ -27,7 +27,7 @@ class MathTest {
     try {
       sqrt(x);  // Expects number.
       return true;
-    } catch (var e) {
+    } catch (e) {
       return false;
     }
   }