Disable two flaky StartSurface{Layout}Tests

BUG=1119527,1120698
TBR=wychen@chromium.org,pmonette@chromium.org

Change-Id: I715f93e12fa221529070db16d83641b6e5f36341
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2373266Reviewed-by: Matthew Wolenetz <wolenetz@chromium.org>
Commit-Queue: Matthew Wolenetz <wolenetz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#801177}

chrome/android/features/start_surface/internal/javatests/src/org/chromium/chrome/features/start_surface/StartSurfaceLayoutTest.java

@@ -1205,6 +1205,7 @@ public class StartSurfaceLayoutTest {
     @Test
     @MediumTest
     @CommandLineFlags.Add({BASE_PARAMS + "/thumbnail_aspect_ratio/2.0/allow_to_refetch/true"})
+    @DisabledTest(message = "http://crbug/1119527 - Flaky on bots.")
     public void testThumbnailFetchingResult_changingAspectRatio() throws Exception {
         prepareTabs(2, 0, mUrl);
         int oldJpegCount = RecordHistogram.getHistogramValueCountForTesting(

chrome/android/features/start_surface/internal/javatests/src/org/chromium/chrome/features/start_surface/StartSurfaceTest.java

@@ -718,6 +718,7 @@ public class StartSurfaceTest {
     @MediumTest
     @Feature({"StartSurface"})
     @CommandLineFlags.Add({BASE_PARAMS + "/single"})
+    @DisabledTest(message = "http://crbug/1120698 - NoInstant_Return version is flaky on bots.")
     public void testSearchInIncognitoSingleSurface() {
         if (!mImmediateReturn) {
             onView(withId(org.chromium.chrome.tab_ui.R.id.home_button)).perform(click());