[heap] Remove some overzealous includes from heap-inl.h.

R=mlippautz@chromium.org

Change-Id: Ic86b8b2bcdedeb148c31a965816a864e8e2b2247
Reviewed-on: https://chromium-review.googlesource.com/789866Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49638}

src/heap/heap-inl.h

@@ -7,14 +7,16 @@
 
 #include <cmath>
 
+// Clients of this interface shouldn't depend on lots of heap internals.
+// Do not include anything from src/heap other than src/heap/heap.h here!
+#include "src/heap/heap.h"
+
 #include "src/base/platform/platform.h"
 #include "src/counters-inl.h"
 #include "src/feedback-vector.h"
-#include "src/heap/heap.h"
+// TODO(mstarzinger): There are 3 more includes to remove in order to no longer
+// leak heap internals to users of this interface!
 #include "src/heap/incremental-marking-inl.h"
-#include "src/heap/mark-compact.h"
-#include "src/heap/object-stats.h"
-#include "src/heap/remembered-set.h"
 #include "src/heap/spaces-inl.h"
 #include "src/heap/store-buffer.h"
 #include "src/isolate.h"