[Start Surface] Fix crash on selecting suggestion from omnibox.

Setting IS_SHOWING_OVERVIEW to false triggers the TasksSurfaceViewBinder to set visibility to GONE.
Setting the TasksSurface visibility to GONE shifts focus to its parent view.
This implicitly unfocuses the LocationBar, which triggers the UrlFocusChangeListeners.
The StartSurface UrlFocusChangeListener calls StartSurface.notifyStateChange().
Here we crash on "assert mPropertyModel.get(IS_SHOWING_OVERVIEW)", since it's already set to false.
Swapping the two lines resolves the issue.

Bug: 982018

Change-Id: I84f8634871c6990ec6440684a7fe53498c38fe14
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1911102
Commit-Queue: Mia Glaese <glamia@chromium.org>
Reviewed-by: Ganggui Tang <gogerald@chromium.org>
Reviewed-by: Yusuf Ozuysal <yusufo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#714766}

chrome/android/features/start_surface/internal/java/src/org/chromium/chrome/features/start_surface/StartSurfaceMediator.java

@@ -344,8 +344,9 @@ class StartSurfaceMediator
     @Override
     public void startedHiding() {
         if (mPropertyModel != null) {
-            mPropertyModel.set(IS_SHOWING_OVERVIEW, false);
             mFakeboxDelegate.removeUrlFocusChangeListener(mUrlFocusChangeListener);
+            mPropertyModel.set(IS_SHOWING_OVERVIEW, false);
+
             destroyFeedSurfaceCoordinator();
         }
         for (StartSurface.OverviewModeObserver observer : mObservers) {