Inserted string validation as separate task in compiler.

frog/tests/leg_only/src/StringEscapeTest.dart

 // Copyright (c) 2012, 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.
 
 // Test that string escapes work correctly.
 
 testSingleCharacterEscapes() {
   List/*<String>*/ examples = [
     "\b\f\n\r\t\v",
     '\b\f\n\r\t\v',
@@ skipping 46 matching lines @@
   List/*<int>*/ values = [0, 1, 0x22, 0x27, 0x5c, 0x7f, 0x80, 0xff,
                           0x100, 0x1000, 0xd7ff, 0xe000, 0xffff];
   for (String s in examples) {
     Expect.equals(values.length, s.length);
     for (int i = 0; i < values.length; i++) {
       Expect.equals(values[i], s.charCodeAt(i));
     }
   }
   // No characters above 0xffff until Leg supports that.
   var long =
-      "\u{0}\u{00}\u{000}\u{0000}\u{00000}\u{000000}\u{0000000}" +
+      "\u{0}\u{00}\u{000}\u{0000}\u{00000}\u{000000}" +
       "\u{1}\u{01}\u{001}\u{00001}" +
-      "\u{ffff}\u{0ffff}\u{00ffff}\u{000ffff}";
-  var longValues = [0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1,
-                    0xffff, 0xffff, 0xffff, 0xffff];
+      "\u{ffff}\u{0ffff}\u{00ffff}";
+  var longValues = [0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 0xffff, 0xffff, 0xffff];
   Expect.equals(longValues.length, long.length);
   for (int i = 0; i < longValues.length; i++) {
     Expect.equals(longValues[i], long.charCodeAt(i));
   }
 }
 
 testIdentityEscapes() {
   // All non-control ASCII characters escaped, except those with special
   // meaning: b, f, n, r, t, u, v, and x (replaced by \x00).
   var asciiLiterals =
@@ skipping 37 matching lines @@
   testUEscapes();
   // Test \b, \f, \n, \r, \t, \v.
   testSingleCharacterEscapes();
   // Test all other single character (identity) escaeps.
   testIdentityEscapes();
   // Test that quotes are handled correctly.
   testQuotes();
   // Test that raw strings are raw.
   testRawStrings();
 }