Revert "Disable flaky tests in StartSurfaceTest"

This reverts commit f9d4d27d.

Reason for revert: the offending CL is already reverted at http://crrev.com/c/2236946.

Original change's description:
> Disable flaky tests in StartSurfaceTest
> 
> TBR=hanxi@chromium.org
> 
> Bug: 1092642
> Change-Id: I434447c3a14e45a4ba6b6b1d911e03bd002239de
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2236737
> Reviewed-by: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
> Commit-Queue: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#776322}

TBR=hanxi@chromium.org,wychen@chromium.org

Change-Id: Iab2fe6f269cf3bc6839719938495ccaf790a94f0
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1092642
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2236949Reviewed-by: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Commit-Queue: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#776329}

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

@@ -453,7 +453,7 @@ public class StartSurfaceLayoutTest {
     }
 
     // From https://stackoverflow.com/a/21505193
-    static boolean isEmulator() {
+    private static boolean isEmulator() {
         return Build.FINGERPRINT.startsWith("generic") || Build.FINGERPRINT.startsWith("unknown")
                 || Build.MODEL.contains("google_sdk") || Build.MODEL.contains("Emulator")
                 || Build.MODEL.contains("Android SDK built for x86")

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

@@ -287,13 +287,8 @@ public class StartSurfaceTest {
     @Test
     @MediumTest
     @Feature({"StartSurface"})
-    @DisableIf.Build(sdk_is_less_than = P, message = "1092642")
     @CommandLineFlags.Add({BASE_PARAMS + "/single"})
     public void testShow_SingleAsHomepage() {
-        if (StartSurfaceLayoutTest.isEmulator()) {
-            // TODO(crbug.com/1092642): Do not skip on emulator.
-            return;
-        }
         if (!mImmediateReturn) {
             onView(withId(org.chromium.chrome.tab_ui.R.id.home_button)).perform(click());
         }
@@ -349,15 +344,10 @@ public class StartSurfaceTest {
     @MediumTest
     @Feature({"StartSurface"})
     // clang-format off
-    @DisableIf.Build(sdk_is_less_than = P, message = "1092642")
     @CommandLineFlags.Add({BASE_PARAMS + "/single" +
         "/exclude_mv_tiles/true/hide_switch_when_no_incognito_tabs/true"})
     public void testShow_SingleAsHomepage_NoMVTiles() {
         // clang-format on
-        if (StartSurfaceLayoutTest.isEmulator()) {
-            // TODO(crbug.com/1092642): Do not skip on emulator.
-            return;
-        }
         if (!mImmediateReturn) {
             onView(withId(org.chromium.chrome.tab_ui.R.id.home_button)).perform(click());
         }
@@ -542,13 +532,8 @@ public class StartSurfaceTest {
     @Test
     @MediumTest
     @Feature({"StartSurface"})
-    @DisableIf.Build(sdk_is_less_than = P, message = "1092642")
     @CommandLineFlags.Add({BASE_PARAMS + "/single"})
     public void testShow_SingleAsTabSwitcher() {
-        if (StartSurfaceLayoutTest.isEmulator()) {
-            // TODO(crbug.com/1092642): Do not skip on emulator.
-            return;
-        }
         if (mImmediateReturn) {
             CriteriaHelper.pollUiThread(
                     ()