Be consistent with number scanning

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/object_store.h"
@@ skipping 347 matching lines @@
   } else {
     while (IsDecimalDigit(c0_)) {
       ReadChar();
     }
     if (c0_ == '.' && !dec_point_seen && IsDecimalDigit(LookaheadChar(1))) {
       Recognize(Token::kDOUBLE);
       while (IsDecimalDigit(c0_)) {
         ReadChar();
       }
     }
-    if ((c0_ == 'e') || (c0_ == 'E')) {
+    if (((c0_ == 'e') || (c0_ == 'E')) &&
+        (IsDecimalDigit(LookaheadChar(1)) ||
+         (LookaheadChar(1) == '-') ||
+         (LookaheadChar(1) == '+'))) {
       Recognize(Token::kDOUBLE);
       if ((c0_ == '-') || (c0_ == '+')) {
         ReadChar();
       }
       if (!IsDecimalDigit(c0_)) {
         ErrorMsg("missing exponent digits");
         return;
       }
       while (IsDecimalDigit(c0_)) {
         ReadChar();
@@ skipping 568 matching lines @@
               "%c%#" Px "", kPrivateKeySeparator, key_value);
   const String& result = String::Handle(String::New(private_key, Heap::kOld));
   return result.raw();
 }
 
 
 void Scanner::InitOnce() {
 }
 
 }  // namespace dart