Revert of Disable platform-mode to try and green up tests.

chrome/android/chrome_public_test_apk.isolate

 # 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.
 {
   'includes': [
     '../../build/android/android.isolate',
     '../chrome_public_test_apk.isolate',
   ],
   'variables': {
     'command': [
       '<(PRODUCT_DIR)/bin/run_chrome_public_test_apk',
+      '--enable-platform-mode',
       '-e', 'local', '--apk-under-test',
       '<(PRODUCT_DIR)/apks/ChromePublic.apk',
     ],
     'files': [
       '../../third_party/proguard/',
       '../chrome_public_test_apk.isolate',
       '<(PRODUCT_DIR)/apks/ChromePublic.apk',
       '<(PRODUCT_DIR)/apks/ChromePublicTest.apk',
       '<(PRODUCT_DIR)/bin/run_chrome_public_test_apk',
       '<(PRODUCT_DIR)/test.lib.java/ChromePublicTest.jar',
     ]
   },
 }