Update from https://crrev.com/318214

build/jni_generator.gypi

 # 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.
 
 # This file is meant to be included into a target to provide a rule
 # to generate jni bindings for Java-files in a consistent manner.
 #
 # To use this, create a gyp target with the following form:
 #  {
 #    'target_name': 'base_jni_headers',
@@ skipping 18 matching lines @@
 
 {
   'variables': {
     'jni_generator': '<(DEPTH)/base/android/jni_generator/jni_generator.py',
     'jni_generator_jarjar_file%': '',
     'jni_generator_ptr_type%': 'long',
     # A comma separated string of include files.
     'jni_generator_includes%': (
         'base/android/jni_generator/jni_generator_helper.h'
     ),
-    'native_exports%': '',
+    'native_exports%': '--native_exports_optional',
   },
   'rules': [
     {
       'rule_name': 'generate_jni_headers',
       'extension': 'java',
       'inputs': [
         '<(jni_generator)',
       ],
       'outputs': [
         '<(SHARED_INTERMEDIATE_DIR)/<(jni_gen_package)/jni/<(RULE_INPUT_ROOT)_jni.h',
@@ skipping 35 matching lines @@
   'hard_dependency': 1,
   'conditions': [
     ['android_webview_build==1', {
       'variables': {
         'native_exports%': '--native_exports',
       },
       'dependencies': [
         '<(DEPTH)/build/android/android_exports.gyp:android_exports',
       ],
     }],
-    ['clang==0', {
-      # Clang builds currently fail with --native_exports_optional due to
-      # http://llvm.org/bugs/show_bug.cgi?id=22602 - only enable for gcc.
-      # http://crbug.com/442327
-      'variables': {
-        'native_exports%': '--native_exports_optional',
-      },
-    }],
   ],
 }