Move most of the implementation of AdjustAmountOfExternalMemory to v8.h

src/heap-inl.h

Index: src/heap-inl.h
diff --git a/src/heap-inl.h b/src/heap-inl.h
index c697fedfdaac2d44da510712ef4e9fcc16df1e74..25acd9adce0cdd70c3cac43549b80484eb867494 100644
--- a/src/heap-inl.h
+++ b/src/heap-inl.h
@@ -532,27 +532,13 @@ int64_t Heap::AdjustAmountOfExternalAllocatedMemory(
   ASSERT(HasBeenSetUp());
   int64_t amount = amount_of_external_allocated_memory_ + change_in_bytes;
   if (change_in_bytes > 0) {
-    // Avoid overflow.

[jochen (gone - plz use gerrit), 2014/06/04 11:53:07]

note that signed overflow is undefined, so these checks all don't make sense

-    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;
-    }
+    amount_of_external_allocated_memory_ = amount;
     int64_t amount_since_last_global_gc = PromotedExternalMemorySize();
-    if (amount_since_last_global_gc > external_allocation_limit_) {
+    if (amount_since_last_global_gc > Internals::kExternalAllocationLimit) {
       CollectAllGarbage(kNoGCFlags, "external memory allocation limit reached");
     }
   } else {
-    // Avoid underflow.
-    if (amount >= 0) {
-      amount_of_external_allocated_memory_ = amount;
-    } else {
-      // Give up and reset the counters in case of an underflow.
-      amount_of_external_allocated_memory_ = 0;
-      amount_of_external_allocated_memory_at_last_global_gc_ = 0;
-    }
+    amount_of_external_allocated_memory_ = amount;
   }
   if (FLAG_trace_external_memory) {
     PrintPID("%8.0f ms: ", isolate()->time_millis_since_init());