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

runtime/bin/process_macos.cc

Index: runtime/bin/process_macos.cc
diff --git a/runtime/bin/process_macos.cc b/runtime/bin/process_macos.cc
index a4420d21251a36e2f4a5bcc0939356760a52ab53..6c0d451712f5bf8f2a48b82a945c9ff00430ce89 100644
--- a/runtime/bin/process_macos.cc
+++ b/runtime/bin/process_macos.cc
@@ -14,6 +14,7 @@
 #endif
 #include <errno.h>   // NOLINT
 #include <fcntl.h>   // NOLINT
+#include <mach/mach.h>  // NOLINT
 #include <poll.h>    // NOLINT
 #include <signal.h>  // NOLINT
 #include <stdio.h>   // NOLINT
@@ -968,6 +969,30 @@ intptr_t Process::CurrentProcessId() {
 }
 
 
+int64_t Process::CurrentRSS() {
+  struct mach_task_basic_info info;
+  mach_msg_type_number_t infoCount = MACH_TASK_BASIC_INFO_COUNT;
+  kern_return_t result =
+      task_info(mach_task_self(), MACH_TASK_BASIC_INFO,
+                reinterpret_cast<task_info_t>(&info), &infoCount);
+  if (result != KERN_SUCCESS) {
+    return -1;
+  }
+  return info.resident_size;
+}
+
+
+int64_t Process::MaxRSS() {
+  struct rusage usage;
+  usage.ru_maxrss = 0;
+  int r = getrusage(RUSAGE_SELF, &usage);
+  if (r < 0) {
+    return -1;
+  }
+  return usage.ru_maxrss;
+}
+
+
 static Mutex* signal_mutex = new Mutex();
 static SignalInfo* signal_handlers = NULL;
 static const int kSignalsCount = 7;