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

runtime/bin/process_android.cc

Index: runtime/bin/process_android.cc
diff --git a/runtime/bin/process_android.cc b/runtime/bin/process_android.cc
index 64ee4dc7497313f30de7c4e6b3a8551f2d162a8c..4da1a7aa455e4ddf61dece64aa1ae53feebf3021 100644
--- a/runtime/bin/process_android.cc
+++ b/runtime/bin/process_android.cc
@@ -887,6 +887,40 @@ intptr_t Process::CurrentProcessId() {
 }
 
 
+intptr_t Process::CurrentRSS() {
+  // The second value in /proc/self/statm is the current RSS in pages.
+  File* statm = File::Open("/proc/self/statm", File::kRead);
+  if (statm == NULL) {
+    return -1;
+  }
+  RefCntReleaseScope<File> releaser(statm);
+  const intptr_t statm_length = 1 * KB;
+  void* buffer = reinterpret_cast<void*>(Dart_ScopeAllocate(statm_length));
+  const intptr_t statm_read = statm->Read(buffer, statm_length);
+  if (statm_read <= 0) {
+    return -1;
+  }
+  intptr_t current_rss_pages = 0;
+  int matches =
+      sscanf(reinterpret_cast<char*>(buffer), "%*s%" Pu "", &current_rss_pages);
+  if (matches != 1) {
+    return -1;
+  }
+  return current_rss_pages * getpagesize();
+}
+
+
+intptr_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 * KB;
+}
+
+
 static Mutex* signal_mutex = new Mutex();
 static SignalInfo* signal_handlers = NULL;
 static const int kSignalsCount = 7;