Re-enable flaky test for OfflinePageUtils

This test was disabled three years back due to flakiness of
ChromeActivityTestRule.loadUrl. Since then a lot has changed,
and possibly this test isn't flaky any more since tons of test
use that method. Reenabling this test and will keep watching
if flakiness returns.

Bug: 786237
Change-Id: I9601394c0fb88617d252e61cf3d8d9d0f8b4da3a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2463571Reviewed-by: David Trainor <dtrainor@chromium.org>
Commit-Queue: Shakti Sahu <shaktisahu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#815859}

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

@@ -25,7 +25,6 @@ import org.chromium.base.ContextUtils;
 import org.chromium.base.task.PostTask;
 import org.chromium.base.test.util.CommandLineFlags;
 import org.chromium.base.test.util.DisableIf;
-import org.chromium.base.test.util.DisabledTest;
 import org.chromium.base.test.util.MetricsUtils.HistogramDelta;
 import org.chromium.base.test.util.UrlUtils;
 import org.chromium.blink.mojom.MhtmlLoadResult;
@@ -211,7 +210,6 @@ public class OfflinePageUtilsTest {
 
     @Test
     @SmallTest
-    @DisabledTest(message = "crbug.com/786237")
     public void testShowOfflineSnackbarIfNecessary() throws Exception {
         // Arrange - build a mock controller for sensing.
         OfflinePageUtils.setSnackbarDurationForTesting(1000);