Allow lazy parsing of eval-created functions

I don't see a reason why we can't benefit from preparsing such functions. We don't necessarily compile them, so fully parsing them when unnecessary is just additional overhead.

BUG=v8:5501

Review-Url: https://codereview.chromium.org/2413213002
Cr-Commit-Position: refs/heads/master@{#40248}

src/ast/scopes.cc

@@ -1119,7 +1119,9 @@ bool Scope::AllowsLazyParsingWithoutUnresolvedVariables() const {
   // inner scopes to find out how to allocate variables on the block scope. At
   // this point, declarations may not have yet been parsed.
   for (const Scope* s = this; s != nullptr; s = s->outer_scope_) {
-    if (s->is_block_scope() || s->is_function_scope()) return false;
+    if (s->is_block_scope()) return false;
+    if (s->is_function_scope()) return false;
+    if (s->is_eval_scope() && is_strict(s->language_mode())) return false;
   }
   return true;
 }

src/parsing/parser.cc

@@ -791,9 +791,6 @@ FunctionLiteral* Parser::DoParseProgram(ParseInfo* info) {
     DCHECK_NOT_NULL(outer);
     parsing_module_ = info->is_module();
     if (info->is_eval()) {
-      if (!outer->is_script_scope() || is_strict(info->language_mode())) {
-        parsing_mode = PARSE_EAGERLY;
-      }
       outer = NewEvalScope(outer);
     } else if (parsing_module_) {
       DCHECK_EQ(outer, info->script_scope());

test/mjsunit/preparse-toplevel-strict-eval.js

+// Copyright 2016 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: --min-preparse-length=0
+
+"use strict";
+var x = 1;
+var g = eval("var y = 100; function h(s) { if (s) x = s; return x+y; }; h");
+
+assertEquals(101, g());
+assertEquals(102, g(2));
+assertEquals(102, g(2));