[Cronet] Move initialization to a new thread rather than the UI thread.

net/android/javatests/src/org/chromium/net/AndroidProxyConfigServiceTestUtil.java

+// Copyright 2017 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.net;
+
+import android.os.Looper;
+
+import org.chromium.base.annotations.CalledByNative;
+
+/**
+ * Utility functions for testing features implemented in ProxyConfigServiceAndroid.
+ */
+public class AndroidProxyConfigServiceTestUtil {
+    /**
+     * Helper for tests that prepares the Looper on the current thread.
+     */
+    @CalledByNative
+    private static void prepareLooper() {
+        Looper.prepare();
+    }
+}