Provide dummy Android UI thread with looper for C++ unit tests

This is is intended for C++ unit tests (e.g. the net unit tests) that don't run
with the UI thread as their main looper, but test code that, on Android, uses Ui
thread events, so need a running Ui thread.

Review URL: https://codereview.chromium.org/1162763004

Cr-Commit-Position: refs/heads/master@{#333734}

base/base.gyp

@@ -992,6 +992,8 @@
         'test/test_switches.h',
         'test/test_timeouts.cc',
         'test/test_timeouts.h',
+        'test/test_ui_thread_android.cc',
+        'test/test_ui_thread_android.h',
         'test/thread_test_helper.cc',
         'test/thread_test_helper.h',
         'test/trace_event_analyzer.cc',
@@ -1409,6 +1411,7 @@
           'type': 'none',
           'sources': [
             'test/android/java/src/org/chromium/base/ContentUriTestUtils.java',
+            'test/android/java/src/org/chromium/base/TestUiThread.java',
           ],
           'variables': {
             'jni_gen_package': 'base',

base/test/BUILD.gn

@@ -114,6 +114,8 @@ source_set("test_support") {
     "test_support_android.h",
     "test_support_ios.h",
     "test_support_ios.mm",
+    "test_ui_thread_android.cc",
+    "test_ui_thread_android.h",
     "thread_test_helper.cc",
     "thread_test_helper.h",
     "trace_event_analyzer.cc",
@@ -205,6 +207,7 @@ if (is_android) {
   generate_jni("base_unittests_jni_headers") {
     sources = [
       "android/java/src/org/chromium/base/ContentUriTestUtils.java",
+      "android/java/src/org/chromium/base/TestUiThread.java",
     ]
     jni_package = "base"
   }

base/test/android/java/src/org/chromium/base/TestUiThread.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.base;
+
+import android.os.Looper;
+
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import javax.annotation.concurrent.ThreadSafe;
+
+/**
+ * Set up a thread as the Chromium UI Thread, and run its looper. This is is intended for C++ unit
+ * tests (e.g. the net unit tests) that don't run with the UI thread as their main looper, but test
+ * code that, on Android, uses UI thread events, so need a running UI thread.
+ */
+@ThreadSafe
+public class TestUiThread {
+    private static final AtomicBoolean sStarted = new AtomicBoolean(false);
+    private static final String TAG = Log.makeTag("TestUiThread");
+
+    @CalledByNative
+    private static void loop() {
+        // @{link ThreadUtils#setUiThread(Looper)} can only be called once in a test run, so do this
+        // once, and leave it running.
+        if (sStarted.getAndSet(true)) return;
+
+        final CountDownLatch startLatch = new CountDownLatch(1);
+        new Thread(new Runnable() {
+
+            @Override
+            public void run() {
+                Looper.prepare();
+                ThreadUtils.setUiThread(Looper.myLooper());
+                startLatch.countDown();
+                Looper.loop();
+            }
+
+        }).start();
+
+        try {
+            startLatch.await();
+        } catch (InterruptedException e) {
+            Log.e(TAG, "Failed to set UI Thread");
+        }
+    }
+}

base/test/test_ui_thread_android.cc

+// 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.
+#include "base/test/test_ui_thread_android.h"
+
+#include "jni/TestUiThread_jni.h"
+
+namespace base {
+
+void StartTestUiThreadLooper() {
+  Java_TestUiThread_loop(base::android::AttachCurrentThread());
+}
+
+bool RegisterTestUiThreadAndroid(JNIEnv* env) {
+  return RegisterNativesImpl(env);
+}
+
+}  // namespace base

base/test/test_ui_thread_android.h

+// 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.
+
+#ifndef BASE_TEST_TEST_UI_THREAD_ANDROID_
+#define BASE_TEST_TEST_UI_THREAD_ANDROID_
+
+#include <jni.h>
+
+namespace base {
+
+// Set up a thread as the Chromium UI Thread, and run its looper. This is is
+// intended for C++ unit tests (e.g. the net unit tests) that don't run with the
+// UI thread as their main looper, but test code that, on Android, uses UI
+// thread events, so need a running UI thread.
+void StartTestUiThreadLooper();
+
+bool RegisterTestUiThreadAndroid(JNIEnv* env);
+}  // namespace base
+
+#endif  //  BASE_TEST_TEST_UI_THREAD_ANDROID_