[TTS] Fix flaky testSecondTapWithSmartSelection.

The ContextualSearchManagerTest testSecondTapWithSmartSelection was
just checking if the panel was closed rather than waiting for it to
close after hiding the panel due to Smart Selection on the second tap.

BUG=778693

Change-Id: Ib403321ec3ac5b4d7a0995bcbd2216bd86c3c9b6
Reviewed-on: https://chromium-review.googlesource.com/742124Reviewed-by: Donn Denman <donnd@chromium.org>
Reviewed-by: Theresa <twellington@chromium.org>
Commit-Queue: Donn Denman <donnd@chromium.org>
Cr-Commit-Position: refs/heads/master@{#513175}

chrome/android/javatests/src/org/chromium/chrome/browser/contextualsearch/ContextualSearchManagerTest.java

@@ -3346,7 +3346,7 @@ public class ContextualSearchManagerTest {
         waitForSelectActionBarVisible();
 
         // Second Tap closes the panel automatically when Smart Selection is active.
-        assertPanelClosedOrUndefined();
+        waitForPanelToClose();
 
         // Sometimes we get an additional Show notification on the second Tap, but not reliably in
         // tests.  See crbug.com/776541.