Update usage of Proguard in clank after moving Proguard to third_party.

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")
 
 assert(is_android)
 
 rebased_android_sdk = rebase_path(android_sdk, root_build_dir)
 rebased_android_sdk_root = rebase_path(android_sdk_root, root_build_dir)
@@ skipping 384 matching lines @@
     testonly = invoker.testonly
   }
 
   _input_jar_path = invoker.input_jar_path
   _output_jar_path = invoker.output_jar_path
   _jar_toc_path = _output_jar_path + ".TOC"
 
   assert(invoker.build_config != "")
 
   if (defined(invoker.proguard_preprocess) && invoker.proguard_preprocess) {
-    _proguard_jar_path = "$android_sdk_root/tools/proguard/lib/proguard.jar"
+    _proguard_jar_path = "//third_party/proguard/lib/proguard.jar"
     _proguard_config_path = invoker.proguard_config
     _build_config = invoker.build_config
     _rebased_build_config = rebase_path(_build_config, root_build_dir)
     _output_jar_target = "${target_name}__proguard_process"
     action(_output_jar_target) {
       script = "//build/android/gyp/proguard.py"
       inputs = [
         android_sdk_jar,
         _proguard_jar_path,
         _build_config,
@@ skipping 1165 matching lines @@
     ]
     args = [
       "--depfile",
       rebase_path(depfile, root_build_dir),
       "--script-output-path",
       rebase_path(generated_script, root_build_dir),
     ]
     args += test_runner_args
   }
 }