Fix typo in gn_isolate_map.pyl.

testing/buildbot/gn_isolate_map.pyl

 ## 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.
 
 # gn_isolate_map.pyl - A mapping of Ninja build target names to GN labels and
 # test type classifications for the tests that are run on the bots.
 #
 # This mapping is used by MB so that we can uniformly refer to test binaries
 # by their Ninja target names in the recipes and not need to worry about how
 # they are referred to in GN or GYP specifically (the GYP target name is pretty
@@ skipping 891 matching lines @@
   },
   "voice_engine_unittests": {
     "label": "//webrtc/voice_engine:voice_engine_unittests",
     "type": "console_test_launcher",
   },
   "webapk_client_junit_tests": {
     "label": "//chrome/android/webapk/libs/client:webapk_client_junit_tests",
     "type": "junit_test",
   },
   "webapk_shell_apk_junit_tests": {
-    "label": "///chrome/android/webapk/shell_apk:webapk_shell_apk_junit_tests",
+    "label": "//chrome/android/webapk/shell_apk:webapk_shell_apk_junit_tests",
     "type": "junit_test",
   },
   "webkit_unit_tests": {
     "label": "//third_party/WebKit/Source/web:webkit_unit_tests",
     "type": "console_test_launcher",
   },
   "wm_unittests": {
     "label": "//ui/wm:wm_unittests",
     "type": "windowed_test_launcher",
   },
   "wtf_unittests": {
     "label": "//third_party/WebKit/Source/wtf:wtf_unittests",
     "type": "console_test_launcher",
   },
   "xmllite_xmpp_unittests": {
     "label": "//webrtc:xmllite_xmpp_unittests",
     "type": "console_test_launcher",
   }
 }