AIX: Fix 'may be used uninitialized' compiler errors

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 36e56a0aba75e8e8e50b558d549885210c23d028..9fbe3b520d613f1f876091901f2e2869c11fec2a 100644
--- a/src/heap/heap-inl.h
+++ b/src/heap/heap-inl.h
@@ -126,7 +126,7 @@ AllocationResult Heap::AllocateOneByteInternalizedString(
   AllocationSpace space = SelectSpace(size, TENURED);
 
   // Allocate string.
-  HeapObject* result;
+  HeapObject* result = nullptr;
   {
     AllocationResult allocation = AllocateRaw(size, space, OLD_SPACE);
     if (!allocation.To(&result)) return allocation;
@@ -158,7 +158,7 @@ AllocationResult Heap::AllocateTwoByteInternalizedString(Vector<const uc16> str,
   AllocationSpace space = SelectSpace(size, TENURED);
 
   // Allocate string.
-  HeapObject* result;
+  HeapObject* result = nullptr;
   {
     AllocationResult allocation = AllocateRaw(size, space, OLD_SPACE);
     if (!allocation.To(&result)) return allocation;
@@ -206,7 +206,7 @@ AllocationResult Heap::AllocateRaw(int size_in_bytes, AllocationSpace space,
   isolate_->counters()->objs_since_last_young()->Increment();
 #endif
 
-  HeapObject* object;
+  HeapObject* object = nullptr;
   AllocationResult allocation;
   if (NEW_SPACE == space) {
     allocation = new_space_.AllocateRaw(size_in_bytes, alignment);