Make org.chromium.chrome.browser.FullscreenActivityTest#testNoIntentWhenInBackground flaky

Chromium Build Sheriffing.

TBR=yusufo@chromium.org

Bug: 906831
Change-Id: Iaa9db6b2cd31ece2c0a84159418ced80d65557cb
Reviewed-on: https://chromium-review.googlesource.com/c/1344610Reviewed-by: Hayato Ito <hayato@chromium.org>
Commit-Queue: Hayato Ito <hayato@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609908}

chrome/android/javatests/src/org/chromium/chrome/browser/FullscreenActivityTest.java

@@ -22,6 +22,7 @@ import org.junit.runner.RunWith;
 import org.chromium.base.Callback;
 import org.chromium.base.ThreadUtils;
 import org.chromium.base.test.util.CommandLineFlags;
+import org.chromium.base.test.util.FlakyTest;
 import org.chromium.chrome.browser.fullscreen.FullscreenOptions;
 import org.chromium.chrome.browser.tab.EmptyTabObserver;
 import org.chromium.chrome.browser.tab.Tab;
@@ -181,6 +182,7 @@ public class FullscreenActivityTest {
      */
     @Test
     @MediumTest
+    @FlakyTest(message = "crbug.com/906831")
     public void testNoIntentWhenInBackground() throws Throwable {
         final Boolean[] isTabFullscreen = new Boolean[1];
         Tab tab = mActivity.getActivityTab();