Add strict mode, sloppy mode and strong mode UseCounters

src/parser.h

 // Copyright 2012 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.
 
 #ifndef V8_PARSER_H_
 #define V8_PARSER_H_
 
 #include "src/allocation.h"
 #include "src/ast.h"
 #include "src/compiler.h"  // TODO(titzer): remove this include dependency
@@ skipping 1182 matching lines @@
                                    Expression* tag);
   uint32_t ComputeTemplateLiteralHash(const TemplateLiteral* lit);
 
   ZoneList<v8::internal::Expression*>* PrepareSpreadArguments(
       ZoneList<v8::internal::Expression*>* list);
   Expression* SpreadCall(Expression* function,
                          ZoneList<v8::internal::Expression*>* args, int pos);
   Expression* SpreadCallNew(Expression* function,
                             ZoneList<v8::internal::Expression*>* args, int pos);
 
+  void SetLanguageMode(Scope* scope, LanguageMode mode);
+  void EnableLanguageMode(LanguageMode mode);

[adamk, 2015/11/03 22:23:15]

These names don't help me understand the difference.

As noted in my comments in parser.cc, I was sort of expecting the use counts to
just be inlined into the prologue parsing, rather than causing a parser
refactor.

[Dan Ehrenberg, 2015/11/03 22:38:34]

I'd like to measure how many webpages are pure strict-mode. I don't see how I
could do that with just prologue parsing.

EnableLanguageMode is a separate cleanup refactoring. I can break it out into a
separate patch if you'd prefer, or if you think it makes things worse rather
than better, I'll just get rid of it. Do you have naming suggestions?

[adamk, 2015/11/03 23:04:17]

I don't follow: how can a page be "pure strict" without a "'use strict'"
prologue?
It doesn't improve readability for me, anyway; the existing code seemed clear,
so I don't really have naming suggestions.

+
   Scanner scanner_;
   PreParser* reusable_preparser_;
   Scope* original_scope_;  // for ES5 function declarations in sloppy eval
   Target* target_stack_;  // for break, continue statements
   ScriptCompiler::CompileOptions compile_options_;
   ParseData* cached_parse_data_;
 
   PendingCompilationErrorHandler pending_error_handler_;
 
   // Other information which will be stored in Parser and moved to Isolate after
@@ skipping 172 matching lines @@
 
 DoExpression* ParserTraits::ParseDoExpression(bool* ok) {
   return parser_->ParseDoExpression(ok);
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PARSER_H_