Fix free memory calculation.

base/sys_info.h

Index: base/sys_info.h
diff --git a/base/sys_info.h b/base/sys_info.h
index e35feff735e4ac3783d1870ae04d711ef7cdd7fc..9cf444a6ee46f8f9a38c2f8a629c8f274279d5de 100644
--- a/base/sys_info.h
+++ b/base/sys_info.h
@@ -18,6 +18,8 @@
 
 namespace base {
 
+struct SystemMemoryInfoKB;
+
 class BASE_EXPORT SysInfo {
  public:
   // Return the number of logical processors/cores on the current machine.
@@ -28,7 +30,14 @@ class BASE_EXPORT SysInfo {
 
   // Return the number of bytes of current available physical memory on the
   // machine.
+  // (The amount of memory that can be allocated without any significant
+  // impact on the system. It can lead to freeing inactive file-backed
+  // and/or speculative file-backed memory).
   static int64_t AmountOfAvailablePhysicalMemory();
+#if defined(OS_LINUX) || defined(OS_ANDROID)
+  static int64_t AmountOfAvailablePhysicalMemory(
+      const SystemMemoryInfoKB& meminfo);
+#endif
 
   // Return the number of bytes of virtual memory of this process. A return
   // value of zero means that there is no limit on the available virtual