Browser: Remove references to android.util.Config

The semantics of Config.DEBUG will be changing soon, and all other
Config.* fields will become deprecated/hidden.

BUG=1780938
diff --git a/src/com/android/browser/ImageGrid.java b/src/com/android/browser/ImageGrid.java
index 9eccb16..9967f36 100644
--- a/src/com/android/browser/ImageGrid.java
+++ b/src/com/android/browser/ImageGrid.java
@@ -17,7 +17,6 @@
 package com.android.browser;
 
 import android.content.Context;
-import android.util.Config;
 import android.view.ContextMenu;
 import android.view.ContextMenu.ContextMenuInfo;
 import android.view.KeyEvent;
@@ -109,7 +108,7 @@
      * @param index Window to remove, from 0 to MAX_TABS-1
      */
     public void remove(int index) {
-        if (Config.DEBUG && (index < 0 || index >= TabControl.MAX_TABS)) {
+        if (Browser.DEBUG && (index < 0 || index >= TabControl.MAX_TABS)) {
             throw new AssertionError();
         }
         mAdapter.remove(index);