Add the Physical Web to Chrome on Android

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

+// Copyright 2015 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.app.Application;
+
+import org.chromium.base.Log;
+import org.chromium.chrome.browser.ChromeApplication;
+
+import java.util.concurrent.atomic.AtomicReference;
+
+/**
+ * This class provides the basic interface to the Physical Web feature.
+ */
+public class PhysicalWebBleClient {

[jdduke (slow), 2015/09/15 16:46:39]

What does "Ble" mean in the class name?

[cco3, 2015/09/16 17:41:28]

Done.

+    private static AtomicReference<PhysicalWebBleClient> sInstance =

[jdduke (slow), 2015/09/15 16:46:39]

Why atomic? Do you expect this to be used on multiple threads?

[cco3, 2015/09/16 17:41:28]

It was just a pattern for singletons that I saw in another class.  Is there a
different pattern you would recommend?

[jdduke (slow), 2015/09/28 22:38:34]

I think a common pattern is something like:

private static class LazyHolder {
    private static final Foo INSTANCE = new Foo();
}

but I guess that won't work here. In any case, this class should only be
accessed from one thread, so we don't really need the atomic guarantees. To make
that concrete you could add a ThreadUtils.assertOnUiThread call at the start of
the function, and just use a regular static member.

[cco3, 2015/09/28 23:20:24]

Done.

+            new AtomicReference<PhysicalWebBleClient>();
+    private static final String TAG = "cr.PhysicalWeb";
+
+    public static PhysicalWebBleClient getInstance(Application application) {
+        if (sInstance.get() == null) {
+            ChromeApplication chromeApplication = (ChromeApplication) application;
+            sInstance.compareAndSet(null, chromeApplication.createPhysicalWebBleClient());
+        }
+        return sInstance.get();
+    }
+
+    void subscribe() {
+        Log.d(TAG, "subscribing in empty client");
+    }
+}