Add MemoryMonitorAndroid

content/browser/memory/memory_monitor_android.h

+// Copyright (c) 2016 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.
+
+#ifndef CONTENT_BROWSER_MEMORY_MEMORY_MONITOR_ANDROID_H_
+#define CONTENT_BROWSER_MEMORY_MEMORY_MONITOR_ANDROID_H_
+
+#include <jni.h>
+
+#include "content/browser/memory/memory_monitor.h"
+
+namespace content {
+
+// A memory monitor for the Android system.
+class CONTENT_EXPORT MemoryMonitorAndroid : public MemoryMonitor {
+ public:
+  static std::unique_ptr<MemoryMonitorAndroid> Create();
+
+  // C++ counter-part of ActivityManager.MemoryInfo
+  struct MemoryInfo {
+    long avail_mem;
+    bool low_memory;
+    long threshold;
+    long total_mem;
+  };
+
+  ~MemoryMonitorAndroid() override;
+
+  // MemoryMonitor implementation:
+  int GetFreeMemoryUntilCriticalMB() override;
+
+  // Returns true when this class can get memory info from the Android system.
+  bool CanGetMemoryInfo();
+  // Get memory info from the Android system.
+  void GetMemoryInfo(MemoryInfo* out);
+
+ private:
+  MemoryMonitorAndroid();
+
+  // Initializes field IDs of ActivityManager.MemoryInfo
+  void InitializeFieldIDs();
+
+  // Field IDs for ActivityManager.MemoryInfo
+  jfieldID avail_mem_id_ = 0;
+  jfieldID low_memory_id_ = 0;
+  jfieldID threshold_id_ = 0;
+  jfieldID total_mem_id_ = 0;
+
+  DISALLOW_COPY_AND_ASSIGN(MemoryMonitorAndroid);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_MEMORY_MEMORY_MONITOR_ANDROID_H_