[heap] Introduce enum of garbage collection reasons.

test/cctest/heap/test-page-promotion.cc

Index: test/cctest/heap/test-page-promotion.cc
diff --git a/test/cctest/heap/test-page-promotion.cc b/test/cctest/heap/test-page-promotion.cc
index a42e315a1c0959c7cd01f006bd74a21907b2feae..70c2783163f97fc23474c71e9aedb8b7982e6c90 100644
--- a/test/cctest/heap/test-page-promotion.cc
+++ b/test/cctest/heap/test-page-promotion.cc
@@ -50,7 +50,7 @@ UNINITIALIZED_TEST(PagePromotion_NewToOld) {
 
     std::vector<Handle<FixedArray>> handles;
     heap::SimulateFullSpace(heap->new_space(), &handles);
-    heap->CollectGarbage(NEW_SPACE);
+    heap->CollectGarbage(NEW_SPACE, i::GarbageCollectionReason::kTesting);
     CHECK_GT(handles.size(), 0u);
     // First object in handle should be on the first page.
     Handle<FixedArray> first_object = handles.front();