Add memory stats for linux page cycler. On linux, we collect

base/process_util_mac.mm

Index: base/process_util_mac.mm
diff --git a/base/process_util_mac.mm b/base/process_util_mac.mm
index bcdaffe9bc23369a823c675be4c7860bd1512794..de59896d9f63b401d59c3f04777a114950dfcd32 100644
--- a/base/process_util_mac.mm
+++ b/base/process_util_mac.mm
@@ -233,4 +233,24 @@ bool ProcessMetrics::GetIOCounters(IoCounters* io_counters) const {
   return false;
 }
 
+size_t ProcessMetrics::GetPagefileUsage() const {
+  NOTIMPLEMENTED();
+  return 0;
+}
+
+size_t ProcessMetrics::GetPeakPagefileUsage() const {
+  NOTIMPLEMENTED();
+  return 0;
+}
+
+size_t ProcessMetrics::GetWorkingSetSize() const {
+  NOTIMPLEMENTED();
+  return 0;
+}
+
+size_t ProcessMetrics::GetPeakWorkingSetSize() const {
+  NOTIMPLEMENTED();
+  return 0;
+}
+
 }  // namespace base