pt 1 in reviving the android build (copied from pm 28a1, wish me luck)

mobile/android/thirdparty/com/squareup/leakcanary/RefWatcher.java

@@ -0,0 +1,20 @@
+/* -*- Mode: Java; c-basic-offset: 4; tab-width: 4; indent-tabs-mode: nil; -*-
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package com.squareup.leakcanary;
+
+/**
+ * No-op implementation of {@link RefWatcher} for release builds. Please use {@link
+ * RefWatcher#DISABLED}.
+ */
+public final class RefWatcher {
+    public static final RefWatcher DISABLED = new RefWatcher();
+
+    private RefWatcher() {}
+
+    public void watch(Object watchedReference) {}
+
+    public void watch(Object watchedReference, String referenceName) {}
+}