Upstream TabTitleObserver

This is a useful class in media playback tests.

BUG=147963

Review URL: https://codereview.chromium.org/985863003

Cr-Commit-Position: refs/heads/master@{#320692}

chrome/test/android/javatests/src/org/chromium/chrome/test/util/browser/TabTitleObserver.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.chrome.test.util.browser;
+
+import android.text.TextUtils;
+
+import org.chromium.base.ThreadUtils;
+import org.chromium.chrome.browser.EmptyTabObserver;
+import org.chromium.chrome.browser.Tab;
+import org.chromium.content.browser.test.util.CallbackHelper;
+
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+
+/**
+ * A utility class to get notified of title change in a tab.
+ */
+public class TabTitleObserver extends EmptyTabObserver {
+    private final String mExpectedTitle;
+    private final CallbackHelper mCallback;
+
+    /**
+     * A constructor.
+     *
+     * @param tab The tab to be observed.
+     * @param expectedTitle The expected title to wait for.
+     */
+    public TabTitleObserver(final Tab tab, final String expectedTitle) {
+        mExpectedTitle = expectedTitle;
+        mCallback = new CallbackHelper();
+        ThreadUtils.runOnUiThreadBlocking(new Runnable() {
+            @Override
+            public void run() {
+                if (!notifyCallbackIfTitleMatches(tab)) {
+                    tab.addObserver(TabTitleObserver.this);
+                }
+            }
+        });
+    }
+
+    /**
+     * Wait for title update up to the given number of seconds.
+     *
+     * @param seconds The number of seconds to wait.
+     * @throws InterruptedException
+     * @throws TimeoutException
+     */
+    public void waitForTitleUpdate(int seconds) throws InterruptedException, TimeoutException {
+        mCallback.waitForCallback(0, 1, seconds, TimeUnit.SECONDS);
+    }
+
+    private boolean notifyCallbackIfTitleMatches(Tab tab) {
+        if (TextUtils.equals(tab.getTitle(), mExpectedTitle)) {
+            mCallback.notifyCalled();
+            return true;
+        }
+        return false;
+    }
+
+    @Override
+    public void onTitleUpdated(Tab tab) {
+        notifyCallbackIfTitleMatches(tab);
+    }
+}
\ No newline at end of file