Re-enable testAutoFetchRequestRetainedOnOtherTabClosed

I ran the test 40 times on my local device, and it passed each one.
Hopefully the previous changes to this test file have fixed the flake.

Bug: 923212
Change-Id: Ic8b3e6e6b82b60d14bdef9975d5d70e256dcf1b7
Reviewed-on: https://chromium-review.googlesource.com/c/1470634Reviewed-by: Carlos Knippschild <carlosk@chromium.org>
Commit-Queue: Dan H <harringtond@google.com>
Cr-Commit-Position: refs/heads/master@{#635255}

chrome/android/javatests/src/org/chromium/chrome/browser/offlinepages/OfflinePageAutoFetchTest.java

@@ -22,7 +22,6 @@ import org.chromium.base.ThreadUtils;
 import org.chromium.base.metrics.RecordHistogram;
 import org.chromium.base.test.util.CallbackHelper;
 import org.chromium.base.test.util.CommandLineFlags;
-import org.chromium.base.test.util.DisabledTest;
 import org.chromium.base.test.util.Feature;
 import org.chromium.chrome.browser.ChromeActivity;
 import org.chromium.chrome.browser.ChromeSwitches;
@@ -263,7 +262,6 @@ public class OfflinePageAutoFetchTest {
     @Test
     @MediumTest
     @Feature({"OfflineAutoFetch"})
-    @DisabledTest(message = "Flaky: https://crbug.com/883486#c20")
     public void testAutoFetchRequestRetainedOnOtherTabClosed() throws Exception {
         startWebServer();
         final String testUrl = mWebServer.getBaseUrl();