[cleanup] Include only what you use.

Bug:v8:6325

Change-Id: Ic829561c013673137c405538c6d7d854b07c36d3
Reviewed-on: https://chromium-review.googlesource.com/490110Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Franziska Hinkelmann <franzih@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45008}

src/heap/heap.h

@@ -6,7 +6,7 @@
 #define V8_HEAP_HEAP_H_
 
 #include <cmath>
-#include <map>
+#include <vector>
 
 // Clients of this interface shouldn't depend on lots of heap internals.
 // Do not include anything from src/heap here!