Fix free memory calculation.

base/sys_info_mac.mm

Index: base/sys_info_mac.mm
diff --git a/base/sys_info_mac.mm b/base/sys_info_mac.mm
index aab1103d4c401d14efc6bf7eecb30c208b9a5d98..1141bd557768bab8eb387dd62668831edd40bd92 100644
--- a/base/sys_info_mac.mm
+++ b/base/sys_info_mac.mm
@@ -19,6 +19,7 @@
 #include "base/mac/scoped_mach_port.h"
 #import "base/mac/sdk_forward_declarations.h"
 #include "base/macros.h"
+#include "base/process/process_metrics.h"
 #include "base/strings/stringprintf.h"
 
 namespace base {
@@ -83,20 +84,12 @@ int64_t SysInfo::AmountOfPhysicalMemory() {
 
 // static
 int64_t SysInfo::AmountOfAvailablePhysicalMemory() {
-  base::mac::ScopedMachSendRight host(mach_host_self());
-  vm_statistics_data_t vm_info;
-  mach_msg_type_number_t count = HOST_VM_INFO_COUNT;
-
-  if (host_statistics(host.get(),
-                      HOST_VM_INFO,
-                      reinterpret_cast<host_info_t>(&vm_info),
-                      &count) != KERN_SUCCESS) {
-    NOTREACHED();
+  SystemMemoryInfoKB info;
+  if (!GetSystemMemoryInfo(&info))
     return 0;
-  }
-
-  return static_cast<int64_t>(vm_info.free_count - vm_info.speculative_count) *
-         PAGE_SIZE;
+  // We should add inactive file-backed memory also but there is no such
+  // information from Mac OS unfortunately.
+  return static_cast<int64_t>(info.free + info.speculative) * 1024;
 }
 
 // static