Remove tidy blacklist for 'script/dom/bindings/*'

Recently, I found myself reading through the Python codegen scripts that
live in 'components/script/dom/bindings/*' and noticed that there were
many tidy violations: unnecessary semicolons, weird spacing, unused
variables, lack of license headers, etc. Considering these files are now
living in our tree and mostly maintained directly by contributors of
Servo (as opposed to being from upstream), I feel these files should not
be excluded from our normal tidy process. This commit removes the
blacklist on these files and fixes all tidy violations.

I added these subdirectories to the blacklist because they appear to be
maintained upstream somewhere else:

* "components/script/dom/bindings/codegen/parser/*",
* "components/script/dom/bindings/codegen/ply/*",

Also, I added a '# noqa' comment which tells us to ignore the
flake8 errors for that line. I chose to ignore this (instead of fixing
it) to make the work for this commit simpler for me.

python/tidy.py

@@ -32,9 +32,10 @@ ignored_files = [
     "python/mozinfo/*",
     "python/mozlog/*",
     "python/toml/*",
+    "components/script/dom/bindings/codegen/parser/*",
+    "components/script/dom/bindings/codegen/ply/*",
 
     # Generated and upstream code combined with our own. Could use cleanup
-    "components/script/dom/bindings/codegen/*",
     "components/style/properties/mod.rs",
     "target/*",
     "ports/gonk/src/native_window_glue.cpp",
@@ -72,7 +73,13 @@ def should_check_reftest(file_name):
     return file_name.endswith(reftest_filetype)
 
 
+EMACS_HEADER = "/* -*- Mode:"
+VIM_HEADER = "/* vim:"
+
+
 def check_license(contents):
+    while contents.startswith(EMACS_HEADER) or contents.startswith(VIM_HEADER):
+        _, _, contents = contents.partition("\n")
     valid_license = any(contents.startswith(license) for license in licenses)
     acknowledged_bad_license = "xfail-license" in contents[:100]
     if not (valid_license or acknowledged_bad_license):