Reland of GN: Enable proguard for apks

chrome/android/chrome_public_apk_tmpl.gni

 # Copyright 2015 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/rules.gni")
 
 # GYP: //chrome/android/chrome_apk.gypi
 template("chrome_public_apk_tmpl") {
   forward_variables_from(invoker, "*")
 
   android_apk(target_name) {
     _native_lib_file =
         rebase_path("$root_gen_dir/CHROME_VERSION.json", root_out_dir)
     native_lib_version_arg = "@FileArg($_native_lib_file:full-quoted)"
 
-    # TODO(GYP):
-    #'proguard_enabled': 'true',
-    #'proguard_flags_paths': [
-    #  'chrome/android/java/proguard.flags',
-    #]
+    if (!is_debug) {
+      proguard_enabled = true
+      proguard_configs = [ "//chrome/android/java/proguard.flags" ]
+    }
 
     if (chromium_linker_supported) {
       use_chromium_linker = true
 
       # TODO: Enable packed relocations for x64. See: b/20532404
       if (current_cpu != "x64") {
         enable_relocation_packing = true
       }
     }
   }
 }