Presubmit should be able to handle files being deleted.

TBR=machenbach@chromium.org

Review-Url: https://codereview.chromium.org/2533583002
Cr-Commit-Position: refs/heads/master@{#41286}

tools/presubmit.py

@@ -179,7 +179,8 @@ class SourceFileProcessor(object):
     all_files = [
       f.AbsoluteLocalPath()
       for f in files
-      if (not self.IgnoreFile(f.LocalPath()) and
+      if (os.path.isfile(f.AbsoluteLocalPath()) and
+          not self.IgnoreFile(f.LocalPath()) and
           self.IsRelevant(f.LocalPath()) and
           all(not self.IgnoreDir(d) for d in dirs(f.LocalPath())) and
           any(map(f.LocalPath().startswith, search_paths)))