[wasm][asm.js] Fix a comment in the asm.js scanner.

src/asmjs/asm-scanner.h

 // Copyright 2017 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_ASMJS_ASM_SCANNER_H_
 #define V8_ASMJS_ASM_SCANNER_H_
 
 #include <memory>
 #include <string>
 #include <unordered_map>
@@ skipping 79 matching lines @@
 
   // Methods to check if the current token is an asm.js "number" (contains a
   // dot) or an "unsigned" (a number without a dot).
   bool IsUnsigned() const { return Token() == kUnsigned; }
   uint64_t AsUnsigned() const { return unsigned_value_; }
   bool IsDouble() const { return Token() == kDouble; }
   double AsDouble() const { return double_value_; }
 
   // clang-format off
   enum {
-    // [-10000 .. -10000-kMaxIdentifierCount)  :: Local identifiers
+    // [-10000-kMaxIdentifierCount, -10000)    :: Local identifiers (counting
+    //                                            backwards)
     // [-10000 .. -1)                          :: Builtin tokens like keywords
     //                                            (also includes some special
     //                                             ones like end of input)
     // 0        .. 255                         :: Single char tokens
     // 256      .. 256+kMaxIdentifierCount     :: Global identifiers
     kLocalsStart = -10000,
 #define V(name, _junk1, _junk2, _junk3) kToken_##name,
     STDLIB_MATH_FUNCTION_LIST(V)
     STDLIB_ARRAY_TYPE_LIST(V)
 #undef V
@@ skipping 38 matching lines @@
 
   // Classify character categories.
   bool IsIdentifierStart(uc32 ch);
   bool IsIdentifierPart(uc32 ch);
   bool IsNumberStart(uc32 ch);
 };
 
 }  // namespace internal
 }  // namespace v8
 #endif