ART: Clean up includes.

Reduce dependencies to improve incremental build times.
Break up circular dependency involving class_linker-inl.h.

Change-Id: I4be742c5c2b5cd9855beea86630fd68aab76b0db
diff --git a/runtime/base/arena_allocator.cc b/runtime/base/arena_allocator.cc
index 59d38ad..b53fa84 100644
--- a/runtime/base/arena_allocator.cc
+++ b/runtime/base/arena_allocator.cc
@@ -20,6 +20,7 @@
 
 #include "arena_allocator.h"
 #include "logging.h"
+#include "mem_map.h"
 #include "mutex.h"
 #include "thread-inl.h"
 #include <memcheck/memcheck.h>
@@ -141,6 +142,10 @@
   size_ = map_->Size();
 }
 
+MemMapArena::~MemMapArena() {
+  // Destroys MemMap via std::unique_ptr<>.
+}
+
 void MemMapArena::Release() {
   if (bytes_allocated_ > 0) {
     map_->MadviseDontNeedAndZero();