Disable access to secondary dex files.

base/android/java/templates/BuildConfig.template

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.base;
 
 /**
  *  Build configuration. Generated on a per-target basis.
  */
 public class BuildConfig {
 
     /** Whether multidex is enabled for this target.
      *
      *  This has to be a function instead of a static final boolean s.t. the initial false value
      *  doesn't get optimized into {@link ChromiumMultiDexInstaller} at base_java compile time.
      */
     public static boolean isMultidexEnabled() {
 #if defined(ENABLE_MULTIDEX)
         return true;
 #else
         return false;
 #endif
     }
 
+    /** Whether this target was built for an official build or not.
+     *
+     *  This has to be a function instead of a static final boolean s.t. the initial false value
+     *  doesn't get optimized into {@link ChromeApplication} at base_java compile time.
+     */
+    public static boolean isOfficialBuild() {
+#if defined(IS_OFFICIAL_BUILD)
+        return true;
+#else
+        return false;
+#endif
+    }
+
     // DCHECK_IS_ON does not change between targets, can be final and optimized out.
 #if defined(_DCHECK_IS_ON)
     public static final boolean DCHECK_IS_ON = true;
 #else
     public static final boolean DCHECK_IS_ON = false;
 #endif
 
     // Sorted list of locales that have a compressed .pak within assets.
     // Stored as an array because AssetManager.list() is slow.
     public static final String[] COMPRESSED_LOCALES =
 #if defined(COMPRESSED_LOCALE_LIST)
       COMPRESSED_LOCALE_LIST;
 #else
       {};
 #endif
 
     // Sorted list of locales that have an uncompressed .pak within assets.
     // Stored as an array because AssetManager.list() is slow.
     public static final String[] UNCOMPRESSED_LOCALES =
 #if defined(UNCOMPRESSED_LOCALE_LIST)
       UNCOMPRESSED_LOCALE_LIST;
 #else
       {};
 #endif
 }