[iwyu] Include handles.h less.

test/cctest/heap/heap-tester.h

Index: test/cctest/heap/heap-tester.h
diff --git a/test/cctest/heap/heap-tester.h b/test/cctest/heap/heap-tester.h
index acfbe92bb6a76652f2394679272400f6473c6c1d..289439c1824be599f29fcc9797423103e2df3a6a 100644
--- a/test/cctest/heap/heap-tester.h
+++ b/test/cctest/heap/heap-tester.h
@@ -5,7 +5,6 @@
 #ifndef HEAP_HEAP_TESTER_H_
 #define HEAP_HEAP_TESTER_H_
 
-#include "src/handles.h"
 #include "src/heap/spaces.h"
 
 // Tests that should have access to private methods of {v8::internal::Heap}.
@@ -56,6 +55,9 @@
 namespace v8 {
 namespace internal {
 
+template <typename T>
+class Handle;
+
 class HeapTester {
  public:
 #define DECLARE_STATIC(Name) static void Test##Name();