[dart:io] Adds ProcessInfo.{max,current}Rss. Adds OS::MaxRSS on Fuchsia.

runtime/vm/os_fuchsia.cc

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
 #if defined(HOST_OS_FUCHSIA)
 
 #include "vm/os.h"
 
 #include <errno.h>
+#include <magenta/process.h>
 #include <magenta/syscalls.h>
+#include <magenta/syscalls/object.h>
 #include <magenta/types.h>
 
 #include "platform/assert.h"
 #include "vm/zone.h"
 
 namespace dart {
 
 #ifndef PRODUCT
 
 DEFINE_FLAG(bool,
@@ skipping 127 matching lines @@
   return false;
 }
 
 
 int OS::NumberOfAvailableProcessors() {
   return sysconf(_SC_NPROCESSORS_CONF);
 }
 
 
 uintptr_t OS::MaxRSS() {
-  // TODO(US-95): Implement.
-  return 0;
+  mx_info_task_stats_t task_stats;
+  mx_handle_t process = mx_process_self();
+  mx_status_t status = mx_object_get_info(
+      process, MX_INFO_TASK_STATS, &task_stats, sizeof(task_stats), NULL, NULL);
+  return (status == NO_ERROR) ? task_stats.mem_committed_bytes : 0;
 }
 
 
 void OS::Sleep(int64_t millis) {
   mx_nanosleep(millis * kMicrosecondsPerMillisecond *
                kNanosecondsPerMicrosecond);
 }
 
 
 void OS::SleepMicros(int64_t micros) {
@@ skipping 140 matching lines @@
 }
 
 
 void OS::Exit(int code) {
   UNIMPLEMENTED();
 }
 
 }  // namespace dart
 
 #endif  // defined(HOST_OS_FUCHSIA)