Fix test crashes I just introduced.

src/runtime.cc

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2426 matching lines @@
       : Heap::AllocateRawTwoByteString(length);
   if (o->IsFailure()) return o;
   String* result = String::cast(o);
   StringShape result_shape(result);
   bool has_changed_character = false;
 
   // Convert all characters to upper case, assuming that they will fit
   // in the buffer
   Access<StringInputBuffer> buffer(&string_input_buffer);
   buffer->Reset(s);
-  unibrow::uchar chars[unibrow::kMaxMappingSize];
+  unibrow::uchar chars[Converter::kMaxWidth];
   int i = 0;
   // We can assume that the string is not empty
   uc32 current = buffer->GetNext();
   while (i < length) {
     bool has_next = buffer->has_more();
     uc32 next = has_next ? buffer->GetNext() : 0;
     int char_length = mapping->get(current, next, chars);
     if (char_length == 0) {
       // The case conversion of this character is the character itself.
       result->Set(result_shape, i, current);
@@ skipping 3414 matching lines @@
   } else {
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     Counters::gc_last_resort_from_js.Increment();
     Heap::CollectAllGarbage();
   }
 }
 
 
 } }  // namespace v8::internal