ART: Swap-space in the compiler

Introduce a swap-space and corresponding allocator to transparently
switch native allocations to memory backed by a file.

Bug: 18596910

(cherry picked from commit 62746d8d9c4400e4764f162b22bfb1a32be287a9)

Change-Id: I131448f3907115054a592af73db86d2b9257ea33
diff --git a/runtime/base/unix_file/fd_file.cc b/runtime/base/unix_file/fd_file.cc
index 780e37a..f272d88 100644
--- a/runtime/base/unix_file/fd_file.cc
+++ b/runtime/base/unix_file/fd_file.cc
@@ -256,4 +256,8 @@
   return (flush_result != 0) ? flush_result : close_result;
 }
 
+void FdFile::MarkUnchecked() {
+  guard_state_ = GuardState::kNoCheck;
+}
+
 }  // namespace unix_file