Use R.txt from AAR to generate R.java for it when building APK.

build/android/gyp/aar.py

 #!/usr/bin/env python
 #
 # Copyright 2016 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.
 
 """Processes an Android AAR file."""
 
 import argparse
 import os
@@ skipping 59 matching lines @@
   if args.list:
     data = {}
     data['aidl'] = []
     data['assets'] = []
     data['resources'] = []
     data['subjars'] = []
     data['subjar_tuples'] = []
     data['has_classes_jar'] = False
     data['has_proguard_flags'] = False
     data['has_native_libraries'] = False
+    data['has_r_text_file'] = False
     with zipfile.ZipFile(aar_file) as z:
       data['is_manifest_empty'] = (
           _IsManifestEmpty(z.read('AndroidManifest.xml')))
 
       for name in z.namelist():
         if name.endswith('/'):
           continue
         if name.startswith('aidl/'):
           data['aidl'].append(name)
         elif name.startswith('res/'):
           data['resources'].append(name)
         elif name.startswith('libs/') and name.endswith('.jar'):
           label = posixpath.basename(name)[:-4]
           label = re.sub(r'[^a-zA-Z0-9._]', '_', label)
           data['subjars'].append(name)
           data['subjar_tuples'].append([label, name])
         elif name.startswith('assets/'):
           data['assets'].append(name)
         elif name.startswith('jni/'):
           data['has_native_libraries'] = True
         elif name == 'classes.jar':
           data['has_classes_jar'] = True
         elif name == 'proguard.txt':
           data['has_proguard_flags'] = True
+        elif name == 'R.txt':
+          # Some AARs, e.g. gvr_controller_java, have empty R.txt. Such AARs
+          # have no resources as well. We treat empty R.txt as having no R.txt.
+          data['has_r_text_file'] = (z.read('R.txt').strip() != '')
 
     print gn_helpers.ToGNString(data)
 
 
 if __name__ == '__main__':
   sys.exit(main())