[asm.js] Fix semicolon insertion in presence of Unicode.

R=clemensh@chromium.org
TEST=mjsunit/asm/regress-920076
BUG=chromium:920076

Change-Id: Ieb6d1dd84ab9434ff17ee09444e7d8ce830f898c
Reviewed-on: https://chromium-review.googlesource.com/c/1402778Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58664}

src/asmjs/asm-parser.cc

@@ -343,7 +343,7 @@ void AsmJsParser::ValidateModule() {
   RECURSE(ValidateModuleParameters());
   EXPECT_TOKEN('{');
   EXPECT_TOKEN(TOK(UseAsm));
-  SkipSemicolon();
+  RECURSE(SkipSemicolon());
   RECURSE(ValidateModuleVars());
   while (Peek(TOK(function))) {
     RECURSE(ValidateFunction());

test/mjsunit/asm/regress-920076.js

+// Copyright 2019 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.
+
+// Flags: --allow-natives-syntax
+
+function Module() {
+  "use asm";
+  function f() {}
+  return f
+}
+eval("(" + Module.toString().replace(/;/, String.fromCharCode(8233)) + ")();");
+assertFalse(%IsAsmWasmCode(Module));  // Valid asm.js, but we reject Unicode.