Add MemoryStateListenerAndroid

components/memory_coordinator/android/java/src/org/chromium/components/memory_coordinator/MemoryStateListener.java

Index: components/memory_coordinator/android/java/src/org/chromium/components/memory_coordinator/MemoryStateListener.java
diff --git a/components/memory_coordinator/android/java/src/org/chromium/components/memory_coordinator/MemoryStateListener.java b/components/memory_coordinator/android/java/src/org/chromium/components/memory_coordinator/MemoryStateListener.java
new file mode 100644
index 0000000000000000000000000000000000000000..b4554068807b22b81fb04154aed5be87db99382f
--- /dev/null
+++ b/components/memory_coordinator/android/java/src/org/chromium/components/memory_coordinator/MemoryStateListener.java
@@ -0,0 +1,66 @@
+// 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.
+
+package org.chromium.components.memory_coordinator;
+
+import android.app.Application;
+import android.content.ComponentCallbacks2;
+import android.content.Context;
+import android.content.res.Configuration;
+
+import org.chromium.base.annotations.CalledByNative;
+import org.chromium.base.annotations.JNINamespace;
+import org.chromium.base.annotations.MainDex;
+
+/**
+ * This class registers a ComponentCallbacks2 which delegates actual memory
+ * management to internal memory coordinator implementation.
+ */
+@JNINamespace("memory_coordinator")
+@MainDex
+public class MemoryStateListener {
+    private static ComponentCallbacks2 sCallbacks = null;
+
+    @CalledByNative
+    private static void registerCallback(Context context) {
+        sCallbacks = new ComponentCallbacks2() {
+                @Override
+                public void onTrimMemory(int level) {
+                    // Though the API document says that we shouldn't compare
+                    // to exact values we filter UI_HIDDEN because it's not
+                    // exactly a memory pressure signal.
+                    if (level != ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN) {
+                        nativeOnTrimMemory(level);
+                    }
+                }
+
+                @Override
+                public void onLowMemory() {
+                    // Don't support old onLowMemory() API.
+                }
+
+                @Override
+                public void onConfigurationChanged(Configuration config) {
+                }
+            };
+        context.registerComponentCallbacks(sCallbacks);
+    }
+
+    @CalledByNative
+    private static void unregisterCallback(Context context) {
+        if (sCallbacks == null) {
+            return;
+        }
+        context.unregisterComponentCallbacks(sCallbacks);
+        sCallbacks = null;
+    }
+
+    @CalledByNative
+    private static void simulateOnTrimMemory(Context context, int level) {
+        Application application = (Application) context.getApplicationContext();
+        application.onTrimMemory(level);
+    }
+
+    private static native void nativeOnTrimMemory(int level);
+}