mac: Fix calulation for number of resident pages in a process.

base/process/process_metrics_win.cc

Index: base/process/process_metrics_win.cc
diff --git a/base/process/process_metrics_win.cc b/base/process/process_metrics_win.cc
index d2f0c935531071a092289637b9696a744c22ea9a..77ac5c626f61cf4221b29f6bfcb5fea1dde00062 100644
--- a/base/process/process_metrics_win.cc
+++ b/base/process/process_metrics_win.cc
@@ -81,7 +81,7 @@ size_t ProcessMetrics::GetPeakWorkingSetSize() const {
 }
 
 bool ProcessMetrics::GetMemoryBytes(size_t* private_bytes,
-                                    size_t* shared_bytes) {
+                                    size_t* shared_bytes) const {
   // PROCESS_MEMORY_COUNTERS_EX is not supported until XP SP2.
   // GetProcessMemoryInfo() will simply fail on prior OS. So the requested
   // information is simply not available. Hence, we will return 0 on unsupported