Remove erroneous DCHECK related to expression classifiers

It seems that I forgot to remove the DCHECK when refactoring this
function, even though the comment had it right.  It also seems that
this is hard to trigger.  The minimal example I found, after fuzzer's
bug, was:

   eval, x[eval]

R=adamk@chromium.org
BUG=chromium:619476
LOG=N

Review-Url: https://codereview.chromium.org/2058413002
Cr-Commit-Position: refs/heads/master@{#36929}

src/parsing/expression-classifier.h

@@ -463,7 +463,6 @@ class ExpressionClassifier {
   // in an inner classifier) or it could be an existing error (in case a
   // copy is needed).
   V8_INLINE void Copy(int i) {
-    DCHECK_LE(reported_errors_end_, i);
     DCHECK_LT(i, reported_errors_->length());
     if (reported_errors_end_ != i)
       reported_errors_->at(reported_errors_end_) = reported_errors_->at(i);

test/mjsunit/regress-crbug-619476.js

+// Copyright 2015 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+var x = {};
+// Crashes in debug mode if an erroneous DCHECK in dfb8d333 is not removed.
+eval, x[eval];