Update to Chromium //base at Chromium commit 3e81715e6d3a4324362635aea46ce1f1a163cca1.

android/java/src/org/chromium/base/annotations/MainDex.java

-// Copyright 2012 The Chromium Authors. All rights reserved.
+// 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.annotations;
 
 import java.lang.annotation.ElementType;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 
 /**
- *  @AccessedByNative is used to ensure proguard will keep this field, since it's
- *  only accessed by native.
+ * An annotation that signals that a class should be kept in the main dex file.
+ *
+ * This generally means it's used by renderer processes, which can't load secondary dexes
+ * on K and below.
  */
-@Target(ElementType.FIELD)
+@Target(ElementType.TYPE)
 @Retention(RetentionPolicy.CLASS)
-public @interface AccessedByNative {
-    public String value() default "";
-}
+public @interface MainDex {}