Add support for calling the java Callback from native.

base/base.gyp

 # Copyright (c) 2012 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.
 
 {
   'variables': {
     'chromium_code': 1,
   },
   'includes': [
     '../build/win_precompile.gypi',
@@ skipping 1365 matching lines @@
       'targets': [
         {
           # GN: //base:base_jni_headers
           'target_name': 'base_jni_headers',
           'type': 'none',
           'sources': [
             'android/java/src/org/chromium/base/ApkAssets.java',
             'android/java/src/org/chromium/base/ApplicationStatus.java',
             'android/java/src/org/chromium/base/AnimationFrameTimeHistogram.java',
             'android/java/src/org/chromium/base/BuildInfo.java',
+            'android/java/src/org/chromium/base/Callback.java',
             'android/java/src/org/chromium/base/CommandLine.java',
             'android/java/src/org/chromium/base/ContentUriUtils.java',
             'android/java/src/org/chromium/base/ContextUtils.java',
             'android/java/src/org/chromium/base/CpuFeatures.java',
             'android/java/src/org/chromium/base/EventLog.java',
             'android/java/src/org/chromium/base/FieldTrialList.java',
             'android/java/src/org/chromium/base/ImportantFileWriterAndroid.java',
             'android/java/src/org/chromium/base/JNIUtils.java',
             'android/java/src/org/chromium/base/JavaHandlerThread.java',
             'android/java/src/org/chromium/base/LocaleUtils.java',
@@ skipping 334 matching lines @@
             '../build/isolate.gypi',
           ],
           'sources': [
             'base_unittests.isolate',
           ],
         },
       ],
     }],
   ],
 }