Move most of the implementation of AdjustAmountOfExternalMemory to v8.h

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index 9f8103c5c5a92b243c42901287698fd57a239110..ab1364715bd67bf7e6bf770d349ead945b96d079 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -6321,10 +6321,9 @@ void V8::SetFailedAccessCheckCallbackFunction(
 }
 
 
-int64_t Isolate::AdjustAmountOfExternalAllocatedMemory(
-    int64_t change_in_bytes) {
-  i::Heap* heap = reinterpret_cast<i::Isolate*>(this)->heap();
-  return heap->AdjustAmountOfExternalAllocatedMemory(change_in_bytes);
+void Isolate::CollectAllGarbage(const char* gc_reason) {
+  reinterpret_cast<i::Isolate*>(this)->heap()->CollectAllGarbage(
+      i::Heap::kNoGCFlags, gc_reason);
 }