[iwyu] Include handles.h less.

src/compilation-cache.h

Index: src/compilation-cache.h
diff --git a/src/compilation-cache.h b/src/compilation-cache.h
index 973673c524335a75e0c3d0cff60c3dba8603ebdf..8b0426974c99cb918750e25584f9bb934aa08e90 100644
--- a/src/compilation-cache.h
+++ b/src/compilation-cache.h
@@ -6,12 +6,14 @@
 #define V8_COMPILATION_CACHE_H_
 
 #include "src/allocation.h"
-#include "src/handles.h"
 #include "src/objects.h"
 
 namespace v8 {
 namespace internal {
 
+template <typename T>
+class Handle;
+
 // The compilation cache consists of several generational sub-caches which uses
 // this class as a base class. A sub-cache contains a compilation cache tables
 // for each generation of the sub-cache. Since the same source code string has