Spec update for Bookmark widget

 Bug: 3286323
 This updates both the assets for the bookmark widget and slightly
 alters its behavior to match the updated spec. There are now two
 touch targets in the header, one launches the browser and the other
 launches the bookmarks view.

Change-Id: I1e8864983852af8421280b86421dea1d9ed4335e
diff --git a/src/com/android/browser/BaseUi.java b/src/com/android/browser/BaseUi.java
index 28a144d..95e795c 100644
--- a/src/com/android/browser/BaseUi.java
+++ b/src/com/android/browser/BaseUi.java
@@ -448,6 +448,9 @@
 
     @Override
     public void showComboView(boolean startWithHistory, Bundle extras) {
+        if (mComboView != null) {
+            return;
+        }
         mComboView = new CombinedBookmarkHistoryView(mActivity,
                 mUiController,
                 startWithHistory ?