Merge "Remove old weak references to callbacks when iterating over callbacks in Communal logic."

import java.lang.ref.WeakReference;

import java.util.ArrayList;

import java.util.Iterator;

import javax.inject.Inject;

    private void executeOnSourceAvailableCallbacks() {

        // If the new source is valid, inform registered Callbacks of its presence.

        for (WeakReference<Callback> callback : mCallbacks) {

            Callback cb = callback.get();

            if (cb != null) {

        Iterator<WeakReference<Callback>> itr = mCallbacks.iterator();

        while (itr.hasNext()) {

            Callback cb = itr.next().get();

            if (cb == null) {

                itr.remove();

            } else {

                cb.onSourceAvailable(

                        (mCommunalEnabled && mCurrentSource != null) ? new WeakReference<>(

                                mCurrentSource) : null);