issue 4817 fixed. Implemented raw strings with 'r' instead of '@' for dart2js

lib/compiler/implementation/scanner/scanner.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.
 
 abstract class Scanner {
   Token tokenize();
 }
 
 /**
  * Common base class for a Dart scanner.
@@ skipping 88 matching lines @@
     return firstToken();
   }
 
   int bigSwitch(int next) {
     beginToken();
     if (next === $TAB || next === $LF || next === $CR || next === $SPACE) {
       appendWhiteSpace(next);
       return advance();
     }
 
+    if ($r === next) {
+      return tokenizeRawStringKeywordOrIdentifier(next);
+    }
+
     if ($a <= next && next <= $z) {
       return tokenizeKeywordOrIdentifier(next, true);
     }
 
     if (($A <= next && next <= $Z) || next === $_ || next === $$) {
       return tokenizeIdentifier(next, byteOffset, true);
     }
 
     if (next === $LT) {
       return tokenizeLessThan(next);
@@ skipping 104 matching lines @@
 
     if (next === $CLOSE_CURLY_BRACKET) {
       return appendEndGroup(CLOSE_CURLY_BRACKET_INFO, "}",
                             OPEN_CURLY_BRACKET_TOKEN);
     }
 
     if (next === $SLASH) {
       return tokenizeSlashOrComment(next);
     }
 
+    // TODO(aprelev@gmail.com) Remove deprecated raw string literals
     if (next === $AT) {
       return tokenizeAtOrRawString(next);
     }
 
     if (next === $DQ || next === $SQ) {
       return tokenizeString(next, byteOffset, false);
     }
 
     if (next === $PERIOD) {
       return tokenizeDotsOrNumber(next);
@@ skipping 370 matching lines @@
         if ($STAR === next) {
           next = advance();
           ++nesting;
         }
       } else {
         next = advance();
       }
     }
   }
 
+  int tokenizeRawStringKeywordOrIdentifier(int next) {
+    int nextnext = peek();
+    if (nextnext === $DQ || nextnext === $SQ) {
+      int start = byteOffset;
+      next = advance();
+      return tokenizeString(next, start, true);
+    }
+    return tokenizeKeywordOrIdentifier(next, true);
+  }
+
   int tokenizeKeywordOrIdentifier(int next, bool allowDollar) {
     KeywordState state = KeywordState.KEYWORD_STATE;
     int start = byteOffset;
     while (state !== null && $a <= next && next <= $z) {
       state = state.next(next);
       next = advance();
     }
     if (state === null || state.keyword === null) {
       return tokenizeIdentifier(next, start, allowDollar);
     }
@@ skipping 220 matching lines @@
       next = advance();
     }
     return error(const SourceString("unterminated string literal"));
   }
 
   int error(SourceString message) {
     appendByteStringToken(BAD_INPUT_INFO, message);
     return advance(); // Ensure progress.
   }
 }