Shortcut the entire meta encoding pre-parse when possible

Author: gsnedders

html5lib/_inputstream.py

@@ -682,6 +682,9 @@ def __init__(self, data):
         self.encoding = None
 
     def getEncoding(self):
+        if b"<meta" not in self.data:
+            return None
+
         methodDispatch = (
             (b"<!--", self.handleComment),
             (b"<meta", self.handleMeta),