Use LocalWPT.test_patch when filtering exportable commits

third_party/WebKit/Tools/Scripts/webkitpy/w3c/local_wpt.py

 # Copyright 2016 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.
 
 """A utility class for interacting with a local checkout of the Web Platform Tests."""
 
 import logging
 
+from webkitpy.common.system.executive import ScriptError
 from webkitpy.w3c.chromium_commit import ChromiumCommit
 
 WPT_REPO_URL = 'https://chromium.googlesource.com/external/w3c/web-platform-tests.git'
 WPT_TMP_DIR = '/tmp/wpt'
 CHROMIUM_WPT_DIR = 'third_party/WebKit/LayoutTests/imported/wpt/'
 
 _log = logging.getLogger(__name__)
 
 
 class LocalWPT(object):
@@ skipping 81 matching lines @@
         patch = patch.replace(CHROMIUM_WPT_DIR, '')
 
         # TODO(jeffcarp): Use git am -p<n> where n is len(CHROMIUM_WPT_DIR.split(/'))
         # or something not off-by-one.
         self.run(['git', 'apply', '-'], input=patch)
         self.run(['git', 'commit', '-am', message])
         self.run(['git', 'push', 'github', branch_name])
 
         return branch_name
 
+    def test_patch(self, patch):
+        """Returns the expected output of a patch against origin/master.
+
+        Args:
+            patch: The patch to test against.
+
+        Returns:
+            A string containing the diff the patch produced.
+        """
+        self.clean()
+
+        # Remove Chromium WPT directory prefix.
+        patch = patch.replace(CHROMIUM_WPT_DIR, '')
+
+        try:
+            self.run(['git', 'apply', '-'], input=patch)
+            self.run(['git', 'add', '.'])
+            output = self.run(['git', 'diff', 'origin/master'])
+        except ScriptError as error:
+            _log.error('Error while applying patch: %s', error)
+            output = ''
+
+        self.clean()
+        return output
+
     def commits_behind_master(self, commit):
         """Returns the number of commits after the given commit on origin/master.
 
         This doesn't include the given commit, and this assumes that the given
         commit is on the the master branch.
         """
         return len(self.run([
             'git', 'rev-list', '{}..origin/master'.format(commit)
         ]).splitlines())