Adding option for Proguard jar to be switched.

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.
 
 import("//build/config/android/config.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/config/zip.gni")
 import("//third_party/ijar/ijar.gni")
 
 assert(is_android)
@@ skipping 94 matching lines @@
   action(target_name) {
     set_sources_assignment_filter([])
     forward_variables_from(invoker,
                            [
                              "deps",
                              "data_deps",
                              "public_deps",
                              "testonly",
                            ])
     script = "//build/android/gyp/proguard.py"
-    _proguard_jar_path = "//third_party/proguard/lib/proguard.jar"
+    if (defined(invoker.proguard_jar_path)) {
+      _proguard_jar_path = invoker.proguard_jar_path
+    } else {
+      _proguard_jar_path = "//third_party/proguard/lib/proguard.jar"
+    }
     _output_jar_path = invoker.output_jar_path
     inputs = [
       _proguard_jar_path,
     ]
     if (defined(invoker.alternative_android_sdk_jar)) {
       inputs += [ invoker.alternative_android_sdk_jar ]
       _rebased_android_sdk_jar =
           rebase_path(invoker.alternative_android_sdk_jar)
     } else {
       inputs += [ android_sdk_jar ]
@@ skipping 2197 matching lines @@
 
     args = [
       "--depfile",
       rebase_path(depfile, root_build_dir),
       "--script-output-path",
       rebase_path(generated_script, root_build_dir),
     ]
     args += test_runner_args
   }
 }