Add --accept-crbug-539509 flag to run-webkit-tests

third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/run_webkit_tests.py

Index: third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/run_webkit_tests.py
diff --git a/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/run_webkit_tests.py b/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/run_webkit_tests.py
index ab51899fdfed89307ee3e1589cb3622d0a7f5464..9e4ae499a3b0d70be6b86a03c301bb171da2d043 100644
--- a/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/run_webkit_tests.py
+++ b/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/run_webkit_tests.py
@@ -61,10 +61,9 @@ def main(argv, stdout, stderr):
 
     try:
         # TODO: crbug.com/539509 - Drop this check and make --target work properly.
-        if options.configuration not in (None, 'Debug', 'Release', 'Debug_x64', 'Release_x64'):
-            raise NotImplementedError('--target must be either "Debug" or "Release"; other values do not work\n.'
-                                      'Use multiple //out directories for multiple builds if necessary.\n'
-                                      'See crbug.com/539509.')
+        if options.configuration not in (None, 'Debug', 'Release', 'Debug_x64', 'Release_x64') and not options.accept_crbug_539509:
+            raise NotImplementedError('--target must be either "Debug" or "Release"; other values do not work, see https://crbug.com/539509.\n'
+                                      'Pass --accept-crbug-539509 to override this check.\n')
 
         port = host.port_factory.get(options.platform, options)
     except NotImplementedError, e: