Disable ReturnToChromeTest#testInitialScrollIndex on Nexus 5X

Test ReturnToChromeTest#testInitialScrollIndex fails deterministically
on some Nexus 5X bots. Disable them for now.

Bug: 1025241
Change-Id: I1e4732e0ad7534823183e6a1a314f6fe8223dcfe
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1919426Reviewed-by: Yue Zhang <yuezhanggg@chromium.org>
Commit-Queue: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#715777}

chrome/android/javatests/src/org/chromium/chrome/browser/tasks/ReturnToChromeTest.java

@@ -18,6 +18,7 @@ import org.junit.Test;
 import org.junit.runner.RunWith;
 
 import org.chromium.base.test.util.CommandLineFlags;
+import org.chromium.base.test.util.DisableIf;
 import org.chromium.base.test.util.Feature;
 import org.chromium.base.test.util.Restriction;
 import org.chromium.chrome.browser.ChromeFeatureList;
@@ -109,8 +110,11 @@ public class ReturnToChromeTest {
     @Test
     @SmallTest
     @Feature({"ReturnToChrome", "RenderTest"})
+    // clang-format off
     @CommandLineFlags.Add({BASE_PARAMS + "/" + TAB_SWITCHER_ON_RETURN_MS + "/0"})
+    @DisableIf.Build(hardware_is = "bullhead", message = "https://crbug.com/1025241")
     public void testInitialScrollIndex() throws Exception {
+        // clang-format on
         TabUiTestHelper.prepareTabsWithThumbnail(mActivityTestRule, 10, 0, mUrl);
 
         // Trigger thumbnail capturing for the last tab.