Revert of Canonicalize handles for optimized compilation.

src/identity-map.cc

 // Copyright 2015 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 "src/identity-map.h"
 
 #include "src/heap/heap.h"
 #include "src/heap/heap-inl.h"
 #include "src/zone-containers.h"
 
@@ skipping 133 matching lines @@
         keys_[i] = not_mapped;
         values_[i] = nullptr;
         last_empty = i;
       }
     }
   }
   // Reinsert all the key/value pairs that were in the wrong place.
   for (auto pair : reinsert) {
     int index = InsertIndex(pair.first);
     DCHECK_GE(index, 0);
-    DCHECK_NE(heap_->not_mapped_symbol(), values_[index]);
+    DCHECK_NULL(values_[index]);
     values_[index] = pair.second;
   }
 }
 
 
 void IdentityMapBase::Resize() {
   // Grow the internal storage and reinsert all the key/value pairs.
   int old_size = size_;
   Object** old_keys = keys_;
   void** old_values = values_;
@@ skipping 16 matching lines @@
     DCHECK_GE(index, 0);
     values_[index] = old_values[i];
   }
 
   // Unregister old keys and register new keys.
   heap_->UnregisterStrongRoots(old_keys);
   heap_->RegisterStrongRoots(keys_, keys_ + size_);
 }
 }  // namespace internal
 }  // namespace v8