Don't hide the reparenting tab while detaching

chrome/android/javatests/src/org/chromium/chrome/browser/customtabs/CustomTabActivityTest.java

Index: chrome/android/javatests/src/org/chromium/chrome/browser/customtabs/CustomTabActivityTest.java
diff --git a/chrome/android/javatests/src/org/chromium/chrome/browser/customtabs/CustomTabActivityTest.java b/chrome/android/javatests/src/org/chromium/chrome/browser/customtabs/CustomTabActivityTest.java
index b74be988fcd0bba5be0d64ad69c267d23b2446d4..da6af2a8e3b9926f86f713588761605eb354c94e 100644
--- a/chrome/android/javatests/src/org/chromium/chrome/browser/customtabs/CustomTabActivityTest.java
+++ b/chrome/android/javatests/src/org/chromium/chrome/browser/customtabs/CustomTabActivityTest.java
@@ -1229,6 +1229,13 @@ public class CustomTabActivityTest extends CustomTabActivityTestBase {
         final ActivityMonitor monitor = getInstrumentation().addMonitor(
                 ChromeTabbedActivity.class.getName(), result, false);
         final Tab tabToBeReparented = mActivity.getActivityTab();
+        final CallbackHelper tabHiddenHelper = new CallbackHelper();
+        tabToBeReparented.addObserver(new EmptyTabObserver() {

[gone, 2016/04/26 22:05:38]

This Observer should probably be removed at some point.

[Yusuf, 2016/04/26 22:10:15]

Done.

+            @Override
+            public void onHidden(Tab tab) {
+                tabHiddenHelper.notifyCalled();
+            }
+        });
         ThreadUtils.postOnUiThread(new Runnable() {
             @Override
             public void run() {
@@ -1261,6 +1268,8 @@ public class CustomTabActivityTest extends CustomTabActivityTestBase {
         assertEquals(newActivity.getWindowAndroid(),
                 tabToBeReparented.getContentViewCore().getWindowAndroid());
         assertFalse(tabToBeReparented.getDelegateFactory() instanceof CustomTabDelegateFactory);
+        assertEquals("The tab should never be hidden during the reparenting process",
+                0, tabHiddenHelper.getCallCount());
         return newActivity;
     }