Switch to vectors instead of bare char* arrays.

src/conversions.cc

Index: src/conversions.cc
===================================================================
--- src/conversions.cc	(revision 4542)
+++ src/conversions.cc	(working copy)
@@ -769,9 +769,11 @@
 
       char* decimal_rep;
       bool used_gay_dtoa = false;
-      char fast_dtoa_buffer[kFastDtoaMaximalLength + 1];
+      const int kFastDtoaBufferCapacity = kFastDtoaMaximalLength + 1;
+      char fast_dtoa_buffer[kFastDtoaBufferCapacity];
       int length;
-      if (FastDtoa(v, fast_dtoa_buffer, &sign, &length, &decimal_point)) {
+      if (FastDtoa(v, Vector<char>(fast_dtoa_buffer, kFastDtoaBufferCapacity),
+                   &sign, &length, &decimal_point)) {
         decimal_rep = fast_dtoa_buffer;
       } else {
         decimal_rep = dtoa(v, 0, 0, &decimal_point, &sign, NULL);