Prevent double reporting on hex, strings, and multiline comments.

sdk/lib/_internal/compiler/implementation/scanner/scanner.dart

Index: sdk/lib/_internal/compiler/implementation/scanner/scanner.dart
diff --git a/sdk/lib/_internal/compiler/implementation/scanner/scanner.dart b/sdk/lib/_internal/compiler/implementation/scanner/scanner.dart
index 34cac3a3bacd90757908e5b226a6eba60fa75a7d..8a3880242bc6e7943b3053e65f5b10bf658b23cf 100644
--- a/sdk/lib/_internal/compiler/implementation/scanner/scanner.dart
+++ b/sdk/lib/_internal/compiler/implementation/scanner/scanner.dart
@@ -628,7 +628,8 @@ abstract class AbstractScanner implements Scanner {
         hasDigits = true;
       } else {
         if (!hasDigits) {
-          return unterminated('0x');
+          unterminated('0x', shouldAdvance: false);
+          return next;
         }
         appendSubstringToken(HEXADECIMAL_INFO, start, true);
         return next;
@@ -949,7 +950,6 @@ abstract class AbstractScanner implements Scanner {
 
   int tokenizeSingleLineRawString(int next, int quoteChar, int start) {
     bool asciiOnly = true;
-    next = advance(); // Advance past the quote.
     while (next != $EOF) {
       if (identical(next, quoteChar)) {
         if (!asciiOnly) handleUnicode(start);
@@ -1078,6 +1078,7 @@ abstract class AbstractScanner implements Scanner {
     return unterminated(
         new String.fromCharCodes([quoteChar, quoteChar, quoteChar]));
   }
+
   int unterminatedRawMultiLineString(int quoteChar) {
     return unterminated(
         'r${new String.fromCharCodes([quoteChar, quoteChar, quoteChar])}');