Move several annotations to annotations package.

base/android/java/src/org/chromium/base/UsedByReflection.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 java.lang.annotation.ElementType;
-import java.lang.annotation.Target;
-
-/**
- * Annotation used for marking methods and fields that are called by reflection.
- * Useful for keeping components that would otherwise be removed by Proguard.
- * Use the value parameter to mention a file that calls this method.
- *
- * Note that adding this annotation to a method is not enough to guarantee that
- * it is kept - either its class must be referenced elsewhere in the program, or
- * the class must be annotated with this as well.
- */
-@Target({
-        ElementType.METHOD, ElementType.FIELD, ElementType.TYPE,
-        ElementType.CONSTRUCTOR })
-public @interface UsedByReflection {
-    String value();
-}