Add Linux MemAvailable to SystemMemoryInfoKB

base/process/process_metrics.h

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file contains routines for gathering resource statistics for processes
 // running on the system.
 
 #ifndef BASE_PROCESS_PROCESS_METRICS_H_
 #define BASE_PROCESS_PROCESS_METRICS_H_
 
@@ skipping 254 matching lines @@
 struct BASE_EXPORT SystemMemoryInfoKB {
   SystemMemoryInfoKB();
   SystemMemoryInfoKB(const SystemMemoryInfoKB& other);
 
   // Serializes the platform specific fields to value.
   std::unique_ptr<Value> ToValue() const;
 
   int total;
   int free;
 
+#if defined(OS_LINUX)
+  // This provides an estimate of available memory as described here:
+  // https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=34e431b0ae398fc54ea69ff85ec700722c9da773
+  // NOTE: this is ONLY valid in kernels 3.14 and up.  Its value will always
+  // be 0 in earlier kernel versions.
+  int available;
+#endif
+
 #if !defined(OS_MACOSX)
   int swap_total;
   int swap_free;
 #endif
 
 #if defined(OS_ANDROID) || defined(OS_LINUX)
   int buffers;
   int cached;
   int active_anon;
   int inactive_anon;
@@ skipping 130 matching lines @@
   SystemDiskInfo disk_info_;
 #endif
 #if defined(OS_CHROMEOS)
   SwapInfo swap_info_;
 #endif
 };
 
 }  // namespace base
 
 #endif  // BASE_PROCESS_PROCESS_METRICS_H_