Scan through Nearby when listing PW URLs

chrome/android/java/src/org/chromium/chrome/browser/physicalweb/NearbyForegroundSubscription.java

Index: chrome/android/java/src/org/chromium/chrome/browser/physicalweb/NearbyForegroundSubscription.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/physicalweb/NearbyForegroundSubscription.java b/chrome/android/java/src/org/chromium/chrome/browser/physicalweb/NearbyForegroundSubscription.java
new file mode 100644
index 0000000000000000000000000000000000000000..d32a4b557b91dec8989974ce417bbc9c8388fb17
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/physicalweb/NearbyForegroundSubscription.java
@@ -0,0 +1,58 @@
+// 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.chrome.browser.physicalweb;
+
+import android.content.Context;
+
+import com.google.android.gms.nearby.Nearby;
+import com.google.android.gms.nearby.messages.MessageListener;
+
+
+/**
+ * This class represents a connection to Google Play Services that does foreground
+ * subscription/unsubscription to Nearby Eddystone-URLs.
+ * To use this class, one should:
+ * 1. connect,
+ * 2. subscribe,
+ * 3. unsubscribe,
+ * 4. repeat steps 2-3 as desired, and
+ * 5. disconnect.
+ */
+class NearbyForegroundSubscription extends NearbySubscription {
+    private static final String TAG = "PhysicalWeb";
+    private final MessageListener mMessageListener;
+    private boolean mShouldSubscribe;
+
+    NearbyForegroundSubscription(Context context) {
+        super(context);
+        mMessageListener = PhysicalWebBleClient.getInstance().createForegroundMessageListener();
+        mShouldSubscribe = false;
+    }
+
+    @Override
+    protected void onConnected() {
+        if (mShouldSubscribe) {
+            subscribe();
+        }
+    }
+
+    void subscribe() {
+        if (!getGoogleApiClient().isConnected()) {
+            mShouldSubscribe = true;
+            return;
+        }
+        Nearby.Messages.subscribe(getGoogleApiClient(), mMessageListener, createSubscribeOptions())
+                .setResultCallback(new SimpleResultCallback("foreground subscribe"));
+    }
+
+    void unsubscribe() {
+        if (!getGoogleApiClient().isConnected()) {
+            mShouldSubscribe = false;
+            return;
+        }
+        Nearby.Messages.unsubscribe(getGoogleApiClient(), mMessageListener)
+                .setResultCallback(new SimpleResultCallback("foreground unsubscribe"));
+    }
+}