base: Add ashmem support to base::DiscardableSharedMemory implementation.

base/process/process_metrics_posix.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/process/process_metrics.h"
 
 #include <sys/resource.h>
 #include <sys/time.h>
 
 #include "base/logging.h"
@@ skipping 50 matching lines @@
     }
     limits.rlim_cur = new_limit;
     if (setrlimit(RLIMIT_NOFILE, &limits) != 0) {
       PLOG(INFO) << "Failed to set file descriptor limit";
     }
   } else {
     PLOG(INFO) << "Failed to get file descriptor limit";
   }
 }
 
+size_t GetPageSize() {
+  return getpagesize();
+}
+
 }  // namespace base