[Android] Enable multidex for debug builds of ChromePublic.

base/android/java/src/org/chromium/base/FieldTrialList.java

 // Copyright 2014 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;
 
+import org.chromium.base.annotations.MainDex;
+
 /**
  * Helper to get field trial information.
  */
+@MainDex
 public class FieldTrialList {
 
     private FieldTrialList() {}
 
     /**
      * @param trialName The name of the trial to get the group for.
      * @return The group name chosen for the named trial, or the empty string if the trial does
      *         not exist.
      */
     public static String findFullName(String trialName) {
         return nativeFindFullName(trialName);
     }
 
     /**
      * @param trialName The name of the trial to get the group for.
      * @return Whether the trial exists or not.
      */
     public static boolean trialExists(String trialName) {
         return nativeTrialExists(trialName);
     }
 
     private static native String nativeFindFullName(String trialName);
     private static native boolean nativeTrialExists(String trialName);
 }