Fix ActionBar#isShowing when called before first layout

Fix a regression introduced by the new hide offset API addition where
an action bar height of 0 (not yet measured) would cause the bar to be
considered hidden.

Bug 14574446

Change-Id: Ic8e22923ab59df6078136daa336e074c4b7adaf5

core/java/com/android/internal/app/WindowDecorActionBar.java

@@ -830,7 +830,9 @@ public class WindowDecorActionBar extends ActionBar implements
     }
 
     public boolean isShowing() {
-        return mNowShowing && getHideOffset() < getHeight();
+        final int height = getHeight();
+        // Take into account the case where the bar has a 0 height due to not being measured yet.
+        return mNowShowing && (height == 0 || getHideOffset() < height);
     }
 
     void animateToMode(boolean toActionMode) {