Refactor Bookmark fragment, fixes NPE

 Bug: 2926451
 This change refactors the BrowserBookmarkPage fragment for better
 encapsulation, and updates the CombinedBookmarkHistoryView and
 ShortcutActivity. ShortcutActivity now supports folder navigation
 as well as toggling list or thumbnail view.

Change-Id: Ie8168467e793d60d75c15746f81318cfa7e9f003
diff --git a/src/com/android/browser/BrowserBookmarksAdapter.java b/src/com/android/browser/BrowserBookmarksAdapter.java
index 6478b10..f587f01 100644
--- a/src/com/android/browser/BrowserBookmarksAdapter.java
+++ b/src/com/android/browser/BrowserBookmarksAdapter.java
@@ -113,4 +113,9 @@
         }
         mCurrentView = view;
     }
+
+    @Override
+    public Cursor getItem(int position) {
+        return (Cursor) super.getItem(position);
+    }
 }