Correctly handle AdjustAmountOfExternalAllocatedMemory(0).

src/heap-inl.h

 // 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 442 matching lines @@
     unflattened_strings_length_ += length;
   }
   return str;
 }
 
 
 intptr_t Heap::AdjustAmountOfExternalAllocatedMemory(
     intptr_t change_in_bytes) {
   ASSERT(HasBeenSetUp());
   intptr_t amount = amount_of_external_allocated_memory_ + change_in_bytes;
-  if (change_in_bytes >= 0) {
+  if (change_in_bytes > 0) {
     // Avoid overflow.
     if (amount > amount_of_external_allocated_memory_) {
       amount_of_external_allocated_memory_ = amount;
     } else {
       // Give up and reset the counters in case of an overflow.
       amount_of_external_allocated_memory_ = 0;
       amount_of_external_allocated_memory_at_last_global_gc_ = 0;
     }
     intptr_t amount_since_last_global_gc = PromotedExternalMemorySize();
     if (amount_since_last_global_gc > external_allocation_limit_) {
@@ skipping 330 matching lines @@
 AssertNoAllocation::~AssertNoAllocation() { }
 DisableAssertNoAllocation::DisableAssertNoAllocation() { }
 DisableAssertNoAllocation::~DisableAssertNoAllocation() { }
 
 #endif
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_INL_H_