Fix string escape, recognize escaped newline

runtime/vm/scanner.cc

 // 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.
 
 #include "vm/scanner.h"
 
 #include "platform/assert.h"
 #include "vm/flags.h"
 #include "vm/object.h"
 #include "vm/thread.h"
@@ skipping 499 matching lines @@
         case 'v':
           escape_char = '\v';
           break;
         case 'u':
         case 'x':
           if (!ScanEscapedCodePoint(&escape_char)) {
             EndStringLiteral();
             return;
           }
           break;
-        case '\0':
-          ErrorMsg("illegal escape sequence in string");
-          EndStringLiteral();
-          return;
         default:
+          if ((c0_ == '\0') || (c0_ == '\n') && !string_is_multiline_) {
+            ErrorMsg("unterminated string literal");
+            EndStringLiteral();
+            return;
+          }
           escape_char = c0_;
           break;
       }
       string_chars.Add(escape_char);
     } else if (c0_ == '$' && !is_raw) {
       // Scanned a string piece.
       ASSERT(string_chars.data() != NULL);
       // Strings are canonicalized: Allocate a symbol.
       current_token_.literal = &String::ZoneHandle(
           String::NewSymbol(string_chars.data(), string_chars.length()));
@@ skipping 355 matching lines @@
               "%c%"PRIxPTR, kPrivateKeySeparator, key_value);
   const String& result = String::Handle(String::New(private_key));
   return result.raw();
 }
 
 
 void Scanner::InitOnce() {
 }
 
 }  // namespace dart