Assert external strings in external string table. Remove TODOs.

src/heap.cc

 // Copyright 2012 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 7868 matching lines @@
   }
 }
 
 
 void ExternalStringTable::CleanUp() {
   int last = 0;
   for (int i = 0; i < new_space_strings_.length(); ++i) {
     if (new_space_strings_[i] == heap_->the_hole_value()) {
       continue;
     }
+    ASSERT(new_space_strings_[i]->IsExternalString());
     if (heap_->InNewSpace(new_space_strings_[i])) {
       new_space_strings_[last++] = new_space_strings_[i];
     } else {
       old_space_strings_.Add(new_space_strings_[i]);
     }
   }
   new_space_strings_.Rewind(last);
   new_space_strings_.Trim();
 
   last = 0;
   for (int i = 0; i < old_space_strings_.length(); ++i) {
     if (old_space_strings_[i] == heap_->the_hole_value()) {
       continue;
     }
+    ASSERT(old_space_strings_[i]->IsExternalString());
     ASSERT(!heap_->InNewSpace(old_space_strings_[i]));
     old_space_strings_[last++] = old_space_strings_[i];
   }
   old_space_strings_.Rewind(last);
   old_space_strings_.Trim();
 #ifdef VERIFY_HEAP
   if (FLAG_verify_heap) {
     Verify();
   }
 #endif
@@ skipping 138 matching lines @@
   if (FLAG_concurrent_recompilation) {
     heap_->relocation_mutex_->Lock();
 #ifdef DEBUG
     heap_->relocation_mutex_locked_by_optimizer_thread_ =
         heap_->isolate()->optimizing_compiler_thread()->IsOptimizerThread();
 #endif  // DEBUG
   }
 }
 
 } }  // namespace v8::internal