Reland of Switch Android gtests to use generated wrapper scripts

scripts/slave/recipes/cronet.expected/android_cronet_tester.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "\nimport os, sys\n\nbuild_path = sys.argv[1]\nif os.path.exists(build_path):\n  for (path, dir, files) in os.walk(build_path):\n    for cur_file in files:\n      if cur_file.endswith('index.lock'):\n        path_to_file = os.path.join(path, cur_file)\n        print 'deleting %s' % path_to_file\n        os.remove(path_to_file)\n",
       "[SLAVE_BUILD]"
     ],
     "cwd": "[SLAVE_BUILD]",
     "name": "cleanup index.lock",
@@ skipping 403 matching lines @@
       "--blacklist-file",
       "[SLAVE_BUILD]/src/out/bad_devices.json"
     ],
     "cwd": "[SLAVE_BUILD]",
     "name": "spawn_device_monitor"
   },
   {
     "cmd": [
       "python",
       "-u",
-      "[SLAVE_BUILD]/src/build/android/test_runner.py",
-      "gtest",
-      "-s",
-      "cronet_unittests",
+      "[SLAVE_BUILD]/src/out/Debug/bin/run_cronet_unittests",
       "--blacklist-file",
       "[SLAVE_BUILD]/src/out/bad_devices.json",
       "--verbose",
       "-t",
       "180"
     ],
     "cwd": "[SLAVE_BUILD]",
     "env": {
-      "CHROMIUM_OUTPUT_DIR": "[SLAVE_BUILD]/src/out/Debug",
       "PATH": "[SLAVE_BUILD]/src/third_party/android_tools/sdk/platform-tools:[SLAVE_BUILD]/src/build/android:%(PATH)s"
     },
     "name": "cronet_unittests"
   },
   {
     "cmd": [
       "python",
       "-u",
-      "[SLAVE_BUILD]/src/build/android/test_runner.py",
-      "gtest",
-      "-s",
-      "net_unittests",
+      "[SLAVE_BUILD]/src/out/Debug/bin/run_net_unittests",
       "--blacklist-file",
       "[SLAVE_BUILD]/src/out/bad_devices.json",
       "--verbose",
       "-t",
       "180"
     ],
     "cwd": "[SLAVE_BUILD]",
     "env": {
-      "CHROMIUM_OUTPUT_DIR": "[SLAVE_BUILD]/src/out/Debug",
       "PATH": "[SLAVE_BUILD]/src/third_party/android_tools/sdk/platform-tools:[SLAVE_BUILD]/src/build/android:%(PATH)s"
     },
     "name": "net_unittests"
   },
   {
     "cmd": [
       "python",
       "-u",
       "[SLAVE_BUILD]/src/out/Debug/bin/run_cronet_sample_test_apk",
       "--blacklist-file",
@@ skipping 114 matching lines @@
       "@@@STEP_LOG_LINE@python.inline@  os.remove(report)@@@",
       "@@@STEP_LOG_END@python.inline@@@"
     ]
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]