Made multiline string literals ignore an initial newline.

frog/leg/scanner/token.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.
 
 final int EOF_TOKEN = 0;
 
 final int KEYWORD_TOKEN = $k;
 final int IDENTIFIER_TOKEN = $a;
 final int DOUBLE_TOKEN = $d;
 final int INT_TOKEN = $i;
@@ skipping 143 matching lines @@
   void printOn(StringBuffer sb) {
     sb.add(stringValue);
   }
 
   String toString() => stringValue;
 
   SourceString copyWithoutQuotes(int initial, int terminal) {
     assert(0 <= initial);
     assert(0 <= terminal);
     assert(initial + terminal <= stringValue.length);
-    assert(stringValue.startsWith(["", "'", "@'", "'''", "@'''"][initial]) ||
-           stringValue.startsWith(['', '"', '@"', '"""', '@"""'][initial]));
-    assert(stringValue.endsWith(["", "'", null, "'''"][terminal]) ||
-           stringValue.endsWith(['', '"', null, '"""'][terminal]));
     return new StringWrapper(
         stringValue.substring(initial, stringValue.length - terminal));
   }
 
   bool isEmpty() => stringValue.isEmpty();
 }
 
 class StringCodeIterator implements Iterator<int> {
   final String string;
   int index;
@@ skipping 219 matching lines @@
 final PrecedenceInfo STRING_INTERPOLATION_INFO =
   const PrecedenceInfo(const SourceString('\${'), 0,
                        STRING_INTERPOLATION_TOKEN);
 
 final PrecedenceInfo HEXADECIMAL_INFO =
   const PrecedenceInfo(const SourceString('hexadecimal'), 0, HEXADECIMAL_TOKEN);
 
 // For reporting lexical errors.
 final PrecedenceInfo ERROR_INFO =
   const PrecedenceInfo(const SourceString('?'), 0, UNKNOWN_TOKEN);