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

build/config/android/internal_rules.gni

Index: build/config/android/internal_rules.gni
diff --git a/build/config/android/internal_rules.gni b/build/config/android/internal_rules.gni
index 48fcbc4e71891f8a8c32cedea9a369fe1570c889..cdd9d433f954c1ef571356360972203e0639a8f7 100644
--- a/build/config/android/internal_rules.gni
+++ b/build/config/android/internal_rules.gni
@@ -2530,7 +2530,7 @@ if (enable_java_templates) {
 
     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
 
@@ -2552,7 +2552,7 @@ if (enable_java_templates) {
       outputs = [
         zip_path,
         srcjar_path,
-        r_text_path,
+        r_text_out_path,
       ]
 
       _all_resource_dirs = []
@@ -2615,12 +2615,21 @@ if (enable_java_templates) {
         "--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" ]
       }