[Android] Enable multidex for release builds of chrome_public_test_apk. (RELAND)

chrome/android/BUILD.gn

 # 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("//android_webview/webview_repack_locales_list.gni")
 import("//build/config/android/config.gni")
 import("//build/config/android/rules.gni")
 import("//build/util/process_version.gni")
 import("//chrome/android/chrome_public_apk_tmpl.gni")
 import("//chrome/android/monochrome_android_manifest_jinja_variables.gni")
@@ skipping 862 matching lines @@
     "//third_party/android_support_test_runner:runner_java",
   ]
   additional_apks = [
     "//chrome/android/webapk/libs/runtime_library/javatests/apk_with_webapk_service:apk_with_webapk_service",
     "//chrome/android/webapk/shell_apk:webapk_javatests",
     "//chrome/android/webapk/shell_apk/javatests/dex_optimizer:dex_optimizer_apk",
     "//chrome/test/android/chrome_public_test_support:chrome_public_test_support_apk",
     "//net/android:net_test_support_apk",
   ]
   proguard_enabled = !is_java_debug
+
+  # The test APK contains code from both the APK under test and the
+  # test APK when proguard is enabled. That causes this APK to exceed
+  # the dex limit.
+  enable_multidex = proguard_enabled
 }
 
 if (enable_vr) {
   instrumentation_test_apk("chrome_public_test_vr_apk") {
     apk_name = "ChromePublicTestVr"
     apk_under_test = ":chrome_public_apk"
     android_manifest = chrome_public_test_vr_apk_manifest
     android_manifest_dep = ":chrome_public_test_vr_apk_manifest"
 
     deps = [
@@ skipping 34 matching lines @@
   apk_name = "ChromeSyncShellTest"
   apk_under_test = ":chrome_sync_shell_apk"
   android_manifest = chrome_sync_shell_test_apk_manifest
   android_manifest_dep = ":chrome_sync_shell_test_apk_manifest"
   deps = [
     ":chrome_sync_shell_test_apk_java",
     "//third_party/android_support_test_runner:runner_java",
   ]
   proguard_enabled = !is_java_debug
 }