Use counter for legacy const.

src/parser.cc

 // 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.
 
 #include "src/v8.h"
 
 #include "src/api.h"
 #include "src/ast.h"
 #include "src/bailout-reason.h"
 #include "src/base/platform/platform.h"
@@ skipping 2254 matching lines @@
       ReportMessageAt(location, "strong_var");
       *ok = false;
       return NULL;
     }
     Consume(Token::VAR);
   } else if (peek() == Token::CONST) {
     Consume(Token::CONST);
     if (is_sloppy(language_mode())) {
       mode = CONST_LEGACY;
       init_op = Token::INIT_CONST_LEGACY;
+      ++use_counts_[v8::Isolate::kLegacyConst];

[adamk, 2015/03/31 18:19:32]

Counting each const in a script separately seems a bit odd, especially since
Blink will collapse all these into one. But I guess that's not particularly
problematic. Just wondering if it's intentional that the V8 API for UseCounters
doesn't match how they're used in Blink.

     } else {
       DCHECK(var_context != kStatement);
       mode = CONST;
       init_op = Token::INIT_CONST;
     }
     is_const = true;
     needs_init = true;
   } else if (peek() == Token::LET && is_strict(language_mode())) {
     Consume(Token::LET);
     DCHECK(var_context != kStatement);
@@ skipping 3274 matching lines @@
     } else {
       const uc16* data = reinterpret_cast<const uc16*>(raw_string->raw_data());
       running_hash = StringHasher::ComputeRunningHash(running_hash, data,
                                                       raw_string->length());
     }
   }
 
   return running_hash;
 }
 } }  // namespace v8::internal