Fix gn_helpers' parsing of bools.

build/gn_helpers.py

 # Copyright 2014 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.
 
 """Helper functions useful when writing scripts that integrate with GN.
 
 The main functions are ToGNString and FromGNString which convert between
 serialized GN veriables and Python variables.
 
 To use in a random python file in the build:
@@ skipping 262 matching lines @@
         self.ConsumeWhitespace()
 
     raise GNException("Unterminated list:\n  " + self.input)
 
   def _ConstantFollows(self, constant):
     """Returns true if the given constant follows immediately at the current
     location in the input. If it does, the text is consumed and the function
     returns true. Otherwise, returns false and the current position is
     unchanged."""
     end = self.cur + len(constant)
-    if end >= len(self.input):
+    if end > len(self.input):
       return False  # Not enough room.
     if self.input[self.cur:end] == constant:
       self.cur = end
       return True
     return False