[scanner] Update outdated DCHECK

We recently changed uc32 to be an unsigned type, and with the invalid
marker being static_cast<uc32>(-1) this DCHECK no longer holds. After
this CL it expicitly checks for the invalid marker.

Bug: v8:10568,chromium:1094226
Change-Id: Idd9efe055b38387e3e37b132cb786cca130767b3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2245592
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Auto-Submit: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68333}

src/parsing/scanner.h

@@ -544,7 +544,8 @@ class V8_EXPORT_PRIVATE Scanner {
   }
 
   void PushBack(uc32 ch) {
-    DCHECK_LE(c0_, static_cast<uc32>(unibrow::Utf16::kMaxNonSurrogateCharCode));
+    DCHECK(IsInvalid(c0_) ||
+           base::IsInRange(c0_, 0u, unibrow::Utf16::kMaxNonSurrogateCharCode));
     source_->Back();
     c0_ = ch;
   }

test/mjsunit/regress/regress-1094226.js

+// Copyright 2020 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.
+
+assertThrows(() => eval('<' + '!'));