Marking testSerializationWorksWithoutGarbageCollection as flaky.

chrome/android/javatests/src/org/chromium/chrome/browser/physicalweb/UrlManagerTest.java

Index: chrome/android/javatests/src/org/chromium/chrome/browser/physicalweb/UrlManagerTest.java
diff --git a/chrome/android/javatests/src/org/chromium/chrome/browser/physicalweb/UrlManagerTest.java b/chrome/android/javatests/src/org/chromium/chrome/browser/physicalweb/UrlManagerTest.java
index 90d192061a86855d89b43c6dc3eaf1bc9857073b..c7fffc70ef07c35a3d2e32a7f06ec3fa33df0aa2 100644
--- a/chrome/android/javatests/src/org/chromium/chrome/browser/physicalweb/UrlManagerTest.java
+++ b/chrome/android/javatests/src/org/chromium/chrome/browser/physicalweb/UrlManagerTest.java
@@ -10,6 +10,7 @@ import android.test.InstrumentationTestCase;
 
 import org.chromium.base.ContextUtils;
 import org.chromium.base.test.util.DisabledTest;
+import org.chromium.base.test.util.FlakyTest;
 import org.chromium.base.test.util.RetryOnFailure;
 import org.chromium.content.browser.test.util.Criteria;
 import org.chromium.content.browser.test.util.CriteriaHelper;
@@ -271,6 +272,7 @@ public class UrlManagerTest extends InstrumentationTestCase {
         assertTrue(urlManager.containsInAnyCache(URL2));
     }
 
+    @FlakyTest(message = "https://crbug.com/685471")
     @SmallTest
     @RetryOnFailure
     public void testSerializationWorksWithoutGarbageCollection() throws Exception {