Retain toolbar visibility on resize/orientation.

Bug: 30038684
Change-Id: I72b722adf41f7a010ba120bcebb241c7664f2006
diff --git a/src/com/android/calculator2/CalculatorDisplay.java b/src/com/android/calculator2/CalculatorDisplay.java
index 728fc11..341564d 100644
--- a/src/com/android/calculator2/CalculatorDisplay.java
+++ b/src/com/android/calculator2/CalculatorDisplay.java
@@ -191,7 +191,12 @@
      */
     public void hideToolbar() {
         if (!getForceToolbarVisible()) {
-            post(mHideToolbarRunnable);
+            removeCallbacks(mHideToolbarRunnable);
+            mHideToolbarRunnable.run();
         }
     }
+
+    public boolean isToolbarVisible() {
+        return mToolbar.getVisibility() == View.VISIBLE;
+    }
 }