Flatten the string in StringToDouble function.

src/conversions.h

 // Copyright 2011 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_CONVERSIONS_H_
 #define V8_CONVERSIONS_H_
 
 #include <limits>
 
 #include "src/base/logging.h"
@@ skipping 180 matching lines @@
   return DoubleToInt32(number->Number());
 }
 
 
 inline uint32_t NumberToUint32(Object* number) {
   if (number->IsSmi()) return Smi::cast(number)->value();
   return DoubleToUint32(number->Number());
 }
 
 
-double StringToDouble(UnicodeCache* unicode_cache,
-                      String* string,
-                      int flags,
-                      double empty_string_val = 0.0);
+double StringToDouble(UnicodeCache* unicode_cache, Handle<String> string,
+                      int flags, double empty_string_val = 0.0);
 
 
 inline bool TryNumberToSize(Isolate* isolate,
                             Object* number, size_t* result) {
   SealHandleScope shs(isolate);
   if (number->IsSmi()) {
     int value = Smi::cast(number)->value();
     DCHECK(static_cast<unsigned>(Smi::kMaxValue)
            <= std::numeric_limits<size_t>::max());
     if (value >= 0) {
@@ skipping 19 matching lines @@
                            Object* number) {
   size_t result = 0;
   bool is_valid = TryNumberToSize(isolate, number, &result);
   CHECK(is_valid);
   return result;
 }
 
 } }  // namespace v8::internal
 
 #endif  // V8_CONVERSIONS_H_