Skip commits that don't generate a patch + fixes to get export working

third_party/WebKit/Tools/Scripts/webkitpy/w3c/chromium_commit.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.
 
 from webkitpy.common.memoized import memoized
 from webkitpy.common.webkit_finder import WebKitFinder
 
+WPT_DIR = 'third_party/WebKit/LayoutTests/imported/wpt/'
+
 
 class ChromiumCommit(object):
 
     def __init__(self, host, sha=None, position=None):
         """
         Args:
             host: A Host object
             sha: A Chromium commit SHA
             position: A string of the form:
                     'Cr-Commit-Position: refs/heads/master@{#431915}'
@@ skipping 38 matching lines @@
         ])
 
     def message(self):
         """Returns a string with a commit's subject and body."""
         return self.host.executive.run_command([
             'git', 'show', '--format=%B', '--no-patch', self.sha
         ])
 
     def format_patch(self):
         """Makes a patch with just changes in files in the WPT for a given commit."""
+
+        # Get list of changed files
+        changed_files = self.host.executive.run_command([
+            'git', 'diff-tree', '--name-only', '--no-commit-id', '-r', self.sha,
+            '--', self.absolute_chromium_wpt_dir()
+        ]).splitlines()
+
+        # Remove files on blacklist (MANIFEST.json)
         # TODO(jeffcarp): exclude expectations files
-        # TODO(jeffcarp): exclude manifest files
+        blacklist = ['MANIFEST.json']
+        qualified_blacklist = [WPT_DIR + f for f in blacklist]
+        filtered_files = [f for f in changed_files if f not in qualified_blacklist]
+
+        # Pass those files to format-patch
         return self.host.executive.run_command([
             'git', 'format-patch', '-1', '--stdout',
-            self.sha, self.absolute_chromium_wpt_dir()
-        ])
+            self.sha, '--'
+        ] + filtered_files, cwd=self.absolute_chromium_dir())
 
     @memoized
     def absolute_chromium_wpt_dir(self):
         finder = WebKitFinder(self.host.filesystem)
         return finder.path_from_webkit_base('LayoutTests', 'imported', 'wpt')
+
+    @memoized
+    def absolute_chromium_dir(self):
+        finder = WebKitFinder(self.host.filesystem)
+        return finder.chromium_base()