Flatten the string in StringToDouble function.

src/conversions.cc

 // 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.
 
 #include <limits.h>
 #include <stdarg.h>
 #include <cmath>
 
 #include "src/v8.h"
 
@@ skipping 465 matching lines @@
   if (decimal_pos > 0) result_size++;
   // Allocate result and fill in the parts.
   SimpleStringBuilder builder(result_size + 1);
   builder.AddSubstring(integer_buffer + integer_pos + 1, integer_part_size);
   if (decimal_pos > 0) builder.AddCharacter('.');
   builder.AddSubstring(decimal_buffer, decimal_pos);
   return builder.Finalize();
 }
 
 
-double StringToDouble(UnicodeCache* unicode_cache,
-                      String* string,
-                      int flags,
-                      double empty_string_val) {
-  DisallowHeapAllocation no_gc;
-  String::FlatContent flat = string->GetFlatContent();
-  // ECMA-262 section 15.1.2.3, empty string is NaN
-  if (flat.IsOneByte()) {
-    return StringToDouble(
-        unicode_cache, flat.ToOneByteVector(), flags, empty_string_val);
-  } else {
-    return StringToDouble(
-        unicode_cache, flat.ToUC16Vector(), flags, empty_string_val);
+double StringToDouble(UnicodeCache* unicode_cache, Handle<String> string,
+                      int flags, double empty_string_val) {
+  Handle<String> flattened = String::Flatten(string);
+  {
+    DisallowHeapAllocation no_gc;
+    String::FlatContent flat = flattened->GetFlatContent();
+    DCHECK(flat.IsFlat());
+    // ECMA-262 section 15.1.2.3, empty string is NaN
+    if (flat.IsOneByte()) {
+      return StringToDouble(unicode_cache, flat.ToOneByteVector(), flags,
+                            empty_string_val);
+    } else {
+      return StringToDouble(unicode_cache, flat.ToUC16Vector(), flags,
+                            empty_string_val);
+    }
   }
 }
 
 
 } }  // namespace v8::internal