Add flag to trace the amount of external memory.

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 469 matching lines @@
   } else {
     // Avoid underflow.
     if (amount >= 0) {
       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;
     }
   }
+  if (FLAG_trace_external_memory) {
+    PrintPID("%8.0f ms: ", isolate()->time_millis_since_init());
+    PrintF("Adjust amount of external memory: delta=%6" V8_PTR_PREFIX "d KB, "
+           " amount=%6" V8_PTR_PREFIX "d KB, isolate=0x%08" V8PRIxPTR ".\n",
+           change_in_bytes / 1024, amount_of_external_allocated_memory_ / 1024,
+           reinterpret_cast<intptr_t>(isolate()));
+  }
   ASSERT(amount_of_external_allocated_memory_ >= 0);
   return amount_of_external_allocated_memory_;
 }
 
 
 void Heap::SetLastScriptId(Object* last_script_id) {
   roots_[kLastScriptIdRootIndex] = last_script_id;
 }
 
 
@@ skipping 312 matching lines @@
 AssertNoAllocation::~AssertNoAllocation() { }
 DisableAssertNoAllocation::DisableAssertNoAllocation() { }
 DisableAssertNoAllocation::~DisableAssertNoAllocation() { }
 
 #endif
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_INL_H_