Valgrind fix: always initialize HCheckTableEntry->is_stable_

src/hydrogen-check-elimination.cc

 // Copyright 2013 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 134 matching lines @@
 
  private:
   // Copy state to successor block.
   HCheckTable* Copy(HBasicBlock* succ, HBasicBlock* from_block, Zone* zone) {
     HCheckTable* copy = new(phase_->zone()) HCheckTable(phase_);
     for (int i = 0; i < size_; i++) {
       HCheckTableEntry* old_entry = &entries_[i];
       HCheckTableEntry* new_entry = &copy->entries_[i];
       new_entry->object_ = old_entry->object_;
       new_entry->maps_ = old_entry->maps_->Copy(phase_->zone());
+      new_entry->is_stable_ = old_entry->is_stable_;
       // Keep the check if the existing check's block dominates the successor.
       if (old_entry->check_ != NULL &&
           old_entry->check_->block()->Dominates(succ)) {
         new_entry->check_ = old_entry->check_;
-        new_entry->is_stable_ = old_entry->is_stable_;
       } else {
         // Leave it NULL till we meet a new check instruction for this object
         // in the control flow.
         new_entry->check_ = NULL;
       }
     }
     copy->cursor_ = cursor_;
     copy->size_ = size_;
 
     // Create entries for succ block's phis.
@@ skipping 556 matching lines @@
   PRINT_STAT(removed_cho);
   PRINT_STAT(narrowed);
   PRINT_STAT(loads);
   PRINT_STAT(empty);
   PRINT_STAT(compares_true);
   PRINT_STAT(compares_false);
   PRINT_STAT(transitions);
 }
 
 } }  // namespace v8::internal