Guarantee execution of HistoryFragment replacement.

Fixes: 32807698

Call executePendingTransactions() in showHistoryFragment().

Change-Id: I54f1523550eb672e8999855652d604ccb65c7cdb
diff --git a/src/com/android/calculator2/Calculator.java b/src/com/android/calculator2/Calculator.java
index ea1d445..f13a9ed 100644
--- a/src/com/android/calculator2/Calculator.java
+++ b/src/com/android/calculator2/Calculator.java
@@ -1215,11 +1215,12 @@
             return;
         }
         if (!mDragLayout.isOpen()) {
-            getFragmentManager().beginTransaction()
+            manager.beginTransaction()
                     .replace(R.id.history_frame, mHistoryFragment, HistoryFragment.TAG)
                     .setTransition(transit)
                     .addToBackStack(HistoryFragment.TAG)
                     .commit();
+            manager.executePendingTransactions();
         }
         // TODO: pass current scroll position of result
     }