Add purge all caches to our ashmem wrapper.

src/utils/android/ashmem.cpp

 /*
  * Copyright 2008 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 /*
  * Implementation of the user-space ashmem API for devices, which have our
  * ashmem-enabled kernel. See ashmem-sim.c for the "fake" tmp-based version,
@@ skipping 62 matching lines @@
 int ashmem_unpin_region(int fd, size_t offset, size_t len)
 {
     struct ashmem_pin pin = { offset, len };
     return ioctl(fd, ASHMEM_UNPIN, &pin);
 }
 
 int ashmem_get_size_region(int fd)
 {
   return ioctl(fd, ASHMEM_GET_SIZE, NULL);
 }
+
+int ashmem_purge_all_caches(int fd)
+{
+  return ioctl(fd, ASHMEM_PURGE_ALL_CACHES, NULL);
+}