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

runtime/bin/process_patch.dart

Index: runtime/bin/process_patch.dart
diff --git a/runtime/bin/process_patch.dart b/runtime/bin/process_patch.dart
index 03c0462f2b9b85fda3f5cde74549b09ce2e31331..a4bd45135993bca68f99b1a1f6c682e10fe2702a 100644
--- a/runtime/bin/process_patch.dart
+++ b/runtime/bin/process_patch.dart
@@ -165,6 +165,30 @@ class _ProcessUtils {
   }
 }
 
+@patch
+class ProcessInfo {
+  @patch
+  static int get maxRss {
+    var result = _maxRss();
+    if (result is OSError) {
+      throw result;
+    }
+    return result;
+  }
+
+  @patch
+  static int get currentRss {
+    var result = _currentRss();
+    if (result is OSError) {
+      throw result;
+    }
+    return result;
+  }
+
+  static _maxRss() native "ProcessInfo_MaxRSS";
+  static _currentRss() native "ProcessInfo_CurrentRSS";
+}
+
 class _ProcessStartStatus {
   int _errorCode; // Set to OS error code if process start failed.
   String _errorMessage; // Set to OS error message if process start failed.