Add connectivity check for Android feedback.

chrome/android/java/src/org/chromium/chrome/browser/feedback/ConnectivityChecker.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.browser.feedback;
+
+import org.chromium.base.CalledByNative;
+import org.chromium.base.JNINamespace;
+import org.chromium.base.ThreadUtils;
+import org.chromium.base.VisibleForTesting;
+import org.chromium.chrome.browser.profiles.Profile;
+
+/**
+ * A utility class for checking if the device is currently connected to the Internet.
+ */
+@JNINamespace("chrome::android")
+public final class ConnectivityChecker {
+    private static final String DEFAULT_NO_CONTENT_URL = "http://clients4.google.com/generate_204";
+    private static final long DEFAULT_TIMEOUT_MS = 10000; // 10 seconds.
+
+    /**
+     * A callback for whether the device is currently connected to the Internet.
+     */
+    public interface ConnectivityCheckerCallback {
+        /**
+         * Called when the result of the connectivity check is ready.
+         */
+        void onResult(boolean connected);
+    }
+
+    /**
+     * Starts an asynchronous request for checking whether the device is currently connected to the
+     * Internet. The result passed to the callback denotes whether the attempt to connect to the
+     * server was successfull.
+     *
+     * If the profile or URL is invalid, the callback will be called with false.
+     * The server reply for the URL must respond with HTTP 204 without any redirects for the
+     * connectivity check to be successfull.
+     *
+     * This method takes ownership of the callback object until the callback has happened.
+     * This method must be called on the main thread.
+     * @param profile the context to do the check in.
+     * @param url the URL to connect to.
+     * @param callback the callback which will get the result.
+     */
+    public static void checkConnectivity(Profile profile, ConnectivityCheckerCallback callback) {
+        checkConnectivity(profile, DEFAULT_NO_CONTENT_URL, DEFAULT_TIMEOUT_MS, callback);
+    }
+
+    @VisibleForTesting
+    static void checkConnectivity(Profile profile, String url, long timeoutMs,
+            final ConnectivityCheckerCallback callback) {
+        ThreadUtils.assertOnUiThread();
+        if (profile == null || url == null) {
+            ThreadUtils.runOnUiThread(new Runnable() {

[cjhopman, 2015/05/07 00:09:09]

will the callback always be called on the ui thread?

Can you just crash if one of these is null instead?

[nyquist, 2015/05/07 05:35:46]

Yes. Both the URLFetcher and the timer for timeout use the same thread as they
are created on, and getting the network request context requires us being on the
UI thread, so all this stuff happens on the UI thread.
I personally prefer not crashing and just letting the user fill in the feedback
form without any helpful info from this. I would be OK with changing the
response from a boolean to an enum though, in these failure-cases. That might
even be helpful. I'd rather do that as a follow-up though, and possibly with
some UMA added around it.

[cjhopman, 2015/05/08 18:58:39]

Sure, but I was thinking that handling null profile/url could be pushed up to
the caller. There, they may know that one or the other or both will never be
null.

[nyquist, 2015/05/12 00:42:30]

Done.

+                @Override
+                public void run() {
+                    callback.onResult(false);
+                }
+            });
+            return;
+        }
+        nativeCheckConnectivity(profile, url, timeoutMs, callback);
+    }
+
+    @CalledByNative
+    private static void executeCallback(Object callback, boolean connected) {
+        ((ConnectivityCheckerCallback) callback).onResult(connected);
+    }
+
+    private ConnectivityChecker() {}
+
+    private static native void nativeCheckConnectivity(
+            Profile profile, String url, long timeoutMs, ConnectivityCheckerCallback callback);
+}