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

tests/language/stack_trace_test.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 // Dart test program for testing throw statement
 
 class MyException {
   const MyException(String message) : message_ = message;
   final String message_;
 }
 
 class Helper {
   static int f1(int i) {
     try {
       i = func();
       i = 10;
-    } catch (MyException exception, var stacktrace) {
+    } on MyException catch (exception, stacktrace) {
       i = 50;
       print(exception.message_);
       Expect.equals((stacktrace != null), true);
       print(stacktrace);
     }
     try {
       int j;
       i = func1();
       i = 200;
-    } catch (MyException exception, var stacktrace) {
+    } on MyException catch (exception, stacktrace) {
       i = 50;
       print(exception.message_);
       Expect.equals((stacktrace != null), true);
       print(stacktrace);
     }
     try {
       int j;
       i = func2();
       i = 200;
-    } catch (MyException exception, var stacktrace) {
+    } on MyException catch (exception, stacktrace) {
       i = 50;
       print(exception.message_);
       Expect.equals((stacktrace != null), true);
       print(stacktrace);
     } finally {
       i = i + 800;
     }
     return i;
   }
 
   static int func() {
     int i = 0;
     while (i < 10) {
       i++;
     }
     if (i > 0) {
       throw new MyException("Exception Test for stack trace being printed");
     }
     return 10;
   }
 
   static int func1() {
     try {
       func();
-    } catch (MyException exception) {
+    } on MyException catch (exception) {
       throw new MyException("Exception Test for stack trace being printed");;
     }
     return 10;
   }
 
   static int func2() {
     try {
       func();
-    } catch (MyException exception) {
+    } on MyException catch (exception) {
       throw;
     }
     return 10;
   }
 
 }
 
 class StackTraceTest {
   static testMain() {
     Expect.equals(850, Helper.f1(1));
   }
 }
 
 main() {
   StackTraceTest.testMain();
 }