Never run errorprone on non-Chromium code.

build/host_jar.gypi

 # 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.
 
 # This file is meant to be included into a target to provide a rule to build
 # a JAR file for use on a host in a consistent manner. If a main class is
 # specified, this file will also generate an executable to run the jar in the
 # output folder's /bin/ directory.
 #
 # To use this, create a gyp target with the following form:
@@ skipping 35 matching lines @@
     'excluded_src_paths': [],
     'generated_src_dirs': [],
     'input_jars_paths': [],
     'intermediate_dir': '<(SHARED_INTERMEDIATE_DIR)/<(_target_name)',
     'jar_dir': '<(PRODUCT_DIR)/lib.java',
     'jar_excluded_classes': [],
     'jar_name': '<(_target_name).jar',
     'jar_path': '<(jar_dir)/<(jar_name)',
     'main_class%': '',
     'stamp': '<(intermediate_dir)/jar.stamp',
-    'enable_errorprone%': '0',
+    'conditions': [
+      ['chromium_code == 0', {
+        'enable_errorprone': 0,
+      }],
+    ],
+    'enable_errorprone%': 0,
     'errorprone_exe_path': '<(PRODUCT_DIR)/bin.java/chromium_errorprone',
   },
   'all_dependent_settings': {
     'variables': {
       'input_jars_paths': ['<(jar_path)']
     },
   },
   'actions': [
     {
       'action_name': 'javac_<(_target_name)',
@@ skipping 70 matching lines @@
       ]
     }],
     ['enable_errorprone == 1', {
       'dependencies': [
         '<(DEPTH)/third_party/errorprone/errorprone.gyp:require_errorprone',
       ],
     }],
   ]
 }