[heap] Move IdentityMap data structure out of heap.

src/identity-map.h

Index: src/identity-map.h
diff --git a/src/heap/identity-map.h b/src/identity-map.h
similarity index 96%
rename from src/heap/identity-map.h
rename to src/identity-map.h
index 672ca5a52a7e292a08cc8de8dcd860b9355ba605..2143e24e37b326c35d8b1c082f457d249e7ad059 100644
--- a/src/heap/identity-map.h
+++ b/src/identity-map.h
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef V8_HEAP_IDENTITY_MAP_H_
-#define V8_HEAP_IDENTITY_MAP_H_
+#ifndef V8_IDENTITY_MAP_H_
+#define V8_IDENTITY_MAP_H_
 
 #include "src/handles.h"
 
@@ -95,4 +95,4 @@ class IdentityMap : public IdentityMapBase {
 }
 }  // namespace v8::internal
 
-#endif  // V8_HEAP_IDENTITY_MAP_H_
+#endif  // V8_IDENTITY_MAP_H_