🎠 Have .apk targets copy .mapping file to apks/ directory

build/config/android/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.
 
 import("//build/config/android/config.gni")
 import("//build/config/android/internal_rules.gni")
 import("//build/toolchain/toolchain.gni")
 
 assert(is_android)
 
@@ skipping 1854 matching lines @@
           _apk_under_test_build_config =
               get_label_info(invoker.apk_under_test, "target_gen_dir") + "/" +
               get_label_info(invoker.apk_under_test, "name") + ".build_config"
           _rebased_apk_under_test_build_config =
               rebase_path(_apk_under_test_build_config, root_build_dir)
           args += [ "--tested-apk-info=@FileArg($_rebased_apk_under_test_build_config:deps_info:proguard_info)" ]
         }
       }
       _dex_sources = [ _proguard_output_jar_path ]
       _dex_deps = [ ":$_proguard_target" ]
+
+      _copy_proguard_mapping_target = "${_template_name}__copy_proguard_mapping"
+      copy(_copy_proguard_mapping_target) {
+        sources = [
+          "$_proguard_output_jar_path.mapping",
+        ]
+        outputs = [
+          "$_final_apk_path.mapping",
+        ]
+        deps = [
+          ":$_proguard_target",
+        ]
+      }
     } else {
       if (enable_multidex) {
         _dex_sources = [ _jar_path ]
       } else {
         _dex_sources = [ _lib_dex_path ]
       }
       _dex_deps = [ ":$java_target" ]
     }
 
     dex("$final_dex_target_name") {
@@ skipping 267 matching lines @@
       }
     }
 
     group(target_name) {
       forward_variables_from(invoker,
                              [
                                "data",
                                "data_deps",
                              ])
       public_deps = _final_deps
+
+      # Make the proguard .mapping file easy to find by putting it beside the .apk.
+      if (_proguard_enabled) {
+        deps = [
+          ":$_copy_proguard_mapping_target",
+        ]
+      }
     }
     group("${target_name}_incremental") {
       forward_variables_from(invoker,
                              [
                                "data",
                                "data_deps",
                              ])
       if (!defined(data_deps)) {
         data_deps = []
       }
@@ skipping 361 matching lines @@
     android_library(target_name) {
       chromium_code = false
       java_files = []
       srcjar_deps = [ ":${_template_name}__protoc_java" ]
       deps = [
         "//third_party/android_protobuf:protobuf_nano_javalib",
       ]
     }
   }
 }