Integrate leg as a component in test.py. Also update presubmit script to run tests with leg.

dart/frog/leg/scanner/parser.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.
 
 /**
  * An event generating parser of Dart programs. This parser expects
  * all tokens in a linked list.
  */
 class Parser {
   final Listener listener;
@@ skipping 16 matching lines @@
       switch (token.value) {
         case Keyword.INTERFACE:
           token = parseInterface(token);
           break;
         case Keyword.CLASS:
           token = parseClass(token);
           break;
         case Keyword.TYPEDEF:
           token = parseNamedFunctionAlias(token);
           break;
-        case const SourceString("#"):
-          token = parseLibraryTags(token);
-          break;
         default:
-          token = parseTopLevelMember(token);
+          // TODO(ahe): Work around frog switch bug #314.
+          if (token.value == const SourceString("#")) {
+            token = parseLibraryTags(token);
+          } else {
+            token = parseTopLevelMember(token);
+          }
           break;
       }
     }
   }
 
   Token parseInterface(Token token) {
     listener.beginInterface(token);
     token = parseIdentifier(next(token));
     token = parseTypeVariablesOpt(token);
     token = parseSupertypesClauseOpt(token);
@@ skipping 522 matching lines @@
   }
 
   Token parseBlock(Token token) {
     token = expect(const SourceString('{'), token);
     while (!optional(const SourceString("}"), token)) {
       token = parseStatement(token);
     }
     return expect(const SourceString("}"), token);
   }
 }