Add MemoryMonitorAndroid

content/browser/memory/memory_monitor_android.h

-// Copyright (c) 2016 The Chromium Authors. All rights reserved.
+// Copyright 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();
 
+  static bool Register(JNIEnv* env);
+
   // C++ counter-part of ActivityManager.MemoryInfo
   struct MemoryInfo {
-    long avail_mem;
-    bool low_memory;
-    long threshold;
-    long total_mem;
+    jlong avail_mem;
+    jboolean low_memory;
+    jlong threshold;
+    jlong 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_