Use LocalWPT.test_patch when filtering exportable commits

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

Index: third_party/WebKit/Tools/Scripts/webkitpy/w3c/local_wpt.py
diff --git a/third_party/WebKit/Tools/Scripts/webkitpy/w3c/local_wpt.py b/third_party/WebKit/Tools/Scripts/webkitpy/w3c/local_wpt.py
index d7217c0999415007a3f5e9ea49322a3559e2f160..cec54e988c9e1a70b2aba4256af3a5a8af89c529 100644
--- a/third_party/WebKit/Tools/Scripts/webkitpy/w3c/local_wpt.py
+++ b/third_party/WebKit/Tools/Scripts/webkitpy/w3c/local_wpt.py
@@ -6,6 +6,7 @@
 
 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'
@@ -107,6 +108,31 @@ class LocalWPT(object):
 
         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.