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

build/config/android/internal_rules.gni

 # 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.
 
 # Do not add any imports to non-//build directories here.
 # Some projects (e.g. V8) do not have non-build directories DEPS'ed in.
 import("//build_overrides/build.gni")
 import("//build/config/android/config.gni")
 import("//build/config/dcheck_always_on.gni")
 import("//build/config/sanitizers/sanitizers.gni")
@@ skipping 2512 matching lines @@
     }
   }
 
   # Runs process_resources.py
   template("process_resources") {
     set_sources_assignment_filter([])
     forward_variables_from(invoker, [ "testonly" ])
 
     zip_path = invoker.zip_path
     srcjar_path = invoker.srcjar_path
-    r_text_path = invoker.r_text_path
+    r_text_out_path = invoker.r_text_out_path
     build_config = invoker.build_config
     android_manifest = invoker.android_manifest
 
     non_constant_id = true
     if (defined(invoker.generate_constant_ids) &&
         invoker.generate_constant_ids) {
       non_constant_id = false
     }
 
     action(target_name) {
       forward_variables_from(invoker,
                              [
                                "deps",
                                "visibility",
                              ])
       script = "//build/android/gyp/process_resources.py"
 
       depfile = "$target_gen_dir/$target_name.d"
       outputs = [
         zip_path,
         srcjar_path,
-        r_text_path,
+        r_text_out_path,
       ]
 
       _all_resource_dirs = []
       sources = []
 
       if (defined(invoker.resource_dirs)) {
         _all_resource_dirs += invoker.resource_dirs
 
         # Speed up "gn gen" by short-circuiting the empty directory.
         if (invoker.resource_dirs != [ "//build/android/ant/empty/res" ] &&
@@ skipping 42 matching lines @@
         "--aapt-path",
         _android_aapt_path,
         "--android-manifest",
         rebase_path(android_manifest, root_build_dir),
         "--resource-dirs=$_rebased_all_resource_dirs",
         "--srcjar-out",
         rebase_path(srcjar_path, root_build_dir),
         "--resource-zip-out",
         rebase_path(zip_path, root_build_dir),
         "--r-text-out",
-        rebase_path(r_text_path, root_build_dir),
+        rebase_path(r_text_out_path, root_build_dir),
         "--dependencies-res-zips=@FileArg($rebase_build_config:resources:dependency_zips)",
         "--extra-res-packages=@FileArg($rebase_build_config:resources:extra_package_names)",
         "--extra-r-text-files=@FileArg($rebase_build_config:resources:extra_r_text_files)",
       ]
 
+      if (defined(invoker.r_text_in_path)) {
+        _r_text_in_path = invoker.r_text_in_path
+        inputs += [ _r_text_in_path ]
+        args += [
+          "--r-text-in",
+          rebase_path(_r_text_in_path, root_build_dir),
+        ]
+      }
+
       if (non_constant_id) {
         args += [ "--non-constant-id" ]
       }
 
       if (defined(invoker.custom_package)) {
         args += [
           "--custom-package",
           invoker.custom_package,
         ]
       }
@@ skipping 154 matching lines @@
         rebase_path(root_build_dir, root_build_dir),
         "--packed-libraries-dir",
         rebase_path(_packed_libraries_dir, root_build_dir),
         "--libraries=${invoker.libraries_filearg}",
         "--filelistjson",
         rebase_path(invoker.file_list_json, root_build_dir),
       ]
     }
   }
 }