Revert of Fix free memory calculation.

base/process/process_metrics_mac.cc

Index: base/process/process_metrics_mac.cc
diff --git a/base/process/process_metrics_mac.cc b/base/process/process_metrics_mac.cc
index 6ab43a8289582f1488000f0e4e738d307438374a..a3c2d6a14aa6acbd2e07e9afd6a55a836bbb3f10 100644
--- a/base/process/process_metrics_mac.cc
+++ b/base/process/process_metrics_mac.cc
@@ -16,7 +16,6 @@
 #include "base/mac/mach_logging.h"
 #include "base/mac/scoped_mach_port.h"
 #include "base/memory/ptr_util.h"
-#include "base/numerics/safe_conversions.h"
 #include "base/sys_info.h"
 
 #if !defined(TASK_POWER_INFO)
@@ -80,6 +79,11 @@
 }
 
 }  // namespace
+
+SystemMemoryInfoKB::SystemMemoryInfoKB() : total(0), free(0) {}
+
+SystemMemoryInfoKB::SystemMemoryInfoKB(const SystemMemoryInfoKB& other) =
+    default;
 
 // Getting a mach task from a pid for another process requires permissions in
 // general, so there doesn't really seem to be a way to do these (and spinning
@@ -373,6 +377,7 @@
   return (data.active_count * PAGE_SIZE) / 1024;
 }
 
+// On Mac, We only get total memory and free memory from the system.
 bool GetSystemMemoryInfo(SystemMemoryInfoKB* meminfo) {
   struct host_basic_info hostinfo;
   mach_msg_type_number_t count = HOST_BASIC_INFO_COUNT;
@@ -385,25 +390,17 @@
   DCHECK_EQ(HOST_BASIC_INFO_COUNT, count);
   meminfo->total = static_cast<int>(hostinfo.max_mem / 1024);
 
-  vm_statistics64_data_t vm_info;
-  count = HOST_VM_INFO64_COUNT;
-
-  if (host_statistics64(host.get(), HOST_VM_INFO64,
-                        reinterpret_cast<host_info64_t>(&vm_info),
-                        &count) != KERN_SUCCESS) {
-    return false;
-  }
-  DCHECK_EQ(HOST_VM_INFO64_COUNT, count);
-
-  static_assert(PAGE_SIZE % 1024 == 0, "Invalid page size");
-  meminfo->free = saturated_cast<int>(
-      PAGE_SIZE / 1024 * (vm_info.free_count - vm_info.speculative_count));
-  meminfo->speculative =
-      saturated_cast<int>(PAGE_SIZE / 1024 * vm_info.speculative_count);
-  meminfo->file_backed =
-      saturated_cast<int>(PAGE_SIZE / 1024 * vm_info.external_page_count);
-  meminfo->purgeable =
-      saturated_cast<int>(PAGE_SIZE / 1024 * vm_info.purgeable_count);
+  vm_statistics_data_t vm_info;
+  count = HOST_VM_INFO_COUNT;
+
+  if (host_statistics(host.get(), HOST_VM_INFO,
+                      reinterpret_cast<host_info_t>(&vm_info),
+                      &count) != KERN_SUCCESS) {
+    return false;
+  }
+
+  meminfo->free = static_cast<int>(
+      (vm_info.free_count - vm_info.speculative_count) * PAGE_SIZE / 1024);
 
   return true;
 }