base: Add ashmem support to base::DiscardableSharedMemory implementation.

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 16db44f63f6e94b51034817a3e1eb1c72c72eb68..8e1d250d481d0724cba9973ea31fca2a442b20c4 100644
--- a/base/process/process_metrics_win.cc
+++ b/base/process/process_metrics_win.cc
@@ -284,4 +284,10 @@ size_t GetSystemCommitCharge() {
   return (info.CommitTotal * system_info.dwPageSize) / 1024;
 }
 
+size_t GetPageSize() {
+  SYSTEM_INFO system_info = {};
+  GetSystemInfo(&system_info);
+  return system_info.dwPageSize ? system_info.dwPageSize : 4096;
+}
+
 }  // namespace base