[WebLayer] Add tests for ObserverList

When looking for untested parts of the public WebLayer API, found we
don't have tests for ObserverList. This copies the tests from the //base
version.

//base runs these tests by including them in the content_shell
instrumentation tests, so do the same thing here by including them in
weblayer instrumentation tests.

Change-Id: I7cbacf6efdb8c9f0bcdebc96cafdb7274b392d2c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1903664Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Clark DuVall <cduvall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#713609}

weblayer/public/javatests/BUILD.gn

+# Copyright 2019 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.
+
+import("//build/config/android/config.gni")
+import("//build/config/android/rules.gni")
+
+android_library("weblayer_public_javatests") {
+  testonly = true
+  java_files = [ "org/chromium/weblayer/ObserverListTest.java" ]
+  deps = [
+    "//base:base_java_test_support",
+    "//third_party/junit:junit",
+    "//weblayer/public/java",
+  ]
+}

weblayer/shell/android/BUILD.gn

@@ -192,6 +192,7 @@ instrumentation_test_apk("weblayer_instrumentation_test_apk") {
     "//content/public/test/android:content_java_test_support",
     "//net/android:net_java_test_support",
     "//third_party/android_support_test_runner:runner_java",
+    "//weblayer/public/javatests:weblayer_public_javatests",
   ]
   java_files = [
     "javatests/src/org/chromium/weblayer/test/DataClearingTest.java",