[heap] Introduce enum of garbage collection reasons.

src/heap/heap-inl.h

Index: src/heap/heap-inl.h
diff --git a/src/heap/heap-inl.h b/src/heap/heap-inl.h
index d6e8c838879169b2147562476bfc61284be717e3..15064ac30e184b29faa826899581b843e540f427 100644
--- a/src/heap/heap-inl.h
+++ b/src/heap/heap-inl.h
@@ -716,8 +716,8 @@ void Heap::RemoveAllocationSitePretenuringFeedback(AllocationSite* site) {
       site, static_cast<uint32_t>(bit_cast<uintptr_t>(site)));
 }
 
-
-bool Heap::CollectGarbage(AllocationSpace space, const char* gc_reason,
+bool Heap::CollectGarbage(AllocationSpace space,
+                          GarbageCollectionReason gc_reason,
                           const v8::GCCallbackFlags callbackFlags) {
   const char* collector_reason = NULL;
   GarbageCollector collector = SelectGarbageCollector(space, &collector_reason);