Disable flaky FullscreenVideoTest#testFullscreenDimensions

TBR=peconn@chromium.org,dtrainor@chromium.org
NOTRY=true

Bug: 906840
Change-Id: I3a9627c2095e71ffccc4f4b0a2e0371d73dc670a
Reviewed-on: https://chromium-review.googlesource.com/c/1346304
Commit-Queue: Egor Pasko <pasko@chromium.org>
Reviewed-by: Egor Pasko <pasko@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610048}

chrome/android/javatests/src/org/chromium/chrome/browser/video/FullscreenVideoTest.java

@@ -102,6 +102,7 @@ public class FullscreenVideoTest {
      */
     @Test
     @MediumTest
+    @FlakyTest(message = "crbug.com/906840")
     public void testFullscreenDimensions() throws InterruptedException, TimeoutException {
         String url =
                 mTestServerRule.getServer().getURL("/content/test/data/media/video-player.html");