[Android] Add gyp support for multidex.

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

Index: base/android/java/src/org/chromium/base/annotations/MainDex.java
diff --git a/base/android/java/src/org/chromium/base/annotations/AccessedByNative.java b/base/android/java/src/org/chromium/base/annotations/MainDex.java
similarity index 53%
copy from base/android/java/src/org/chromium/base/annotations/AccessedByNative.java
copy to base/android/java/src/org/chromium/base/annotations/MainDex.java
index 6df7c11027ccf6122b0df4d6c6c8964f835b1526..0b35ade8ee62de8b33a5e75068927a1c431bb1bd 100644
--- a/base/android/java/src/org/chromium/base/annotations/AccessedByNative.java
+++ b/base/android/java/src/org/chromium/base/annotations/MainDex.java
@@ -1,4 +1,4 @@
-// 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.
 
@@ -10,11 +10,12 @@ 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.

[Yaron, 2015/08/05 21:56:41]

So all classes that need to be kept need to have this annotation?

[jbudorick, 2015/08/05 22:55:22]

That or they need to be specified in some other way in main_dex_classes.flags
(or the base mainDexClasses.rules in the sdk).

+ *
+ * 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 {
 }