Revert of 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 ecaa7317faf9e882aecfe90421cd32af18c55aca..e35feff735e4ac3783d1870ae04d711ef7cdd7fc 100644
--- a/base/sys_info.h
+++ b/base/sys_info.h
@@ -13,17 +13,10 @@
 
 #include "base/base_export.h"
 #include "base/files/file_path.h"
-#include "base/gtest_prod_util.h"
 #include "base/time/time.h"
 #include "build/build_config.h"
 
 namespace base {
-
-namespace debug {
-FORWARD_DECLARE_TEST(SystemMetricsTest, ParseMeminfo);
-}
-
-struct SystemMemoryInfoKB;
 
 class BASE_EXPORT SysInfo {
  public:
@@ -35,9 +28,6 @@
 
   // 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();
 
   // Return the number of bytes of virtual memory of this process. A return
@@ -157,15 +147,6 @@
   // Low-end device refers to devices having less than 512M memory in the
   // current implementation.
   static bool IsLowEndDevice();
-
- private:
-  FRIEND_TEST_ALL_PREFIXES(SysInfoTest, AmountOfAvailablePhysicalMemory);
-  FRIEND_TEST_ALL_PREFIXES(debug::SystemMetricsTest, ParseMeminfo);
-
-#if defined(OS_LINUX) || defined(OS_ANDROID)
-  static int64_t AmountOfAvailablePhysicalMemory(
-      const SystemMemoryInfoKB& meminfo);
-#endif
 };
 
 }  // namespace base