<third_party/WebKit> FIXUP: Prevent a python IOError on Windows

The bison script for compiling grammars suffers from the MAX_PATH IOError
issue on Windows. This occurs when doing a shadow build that results in
large relative paths in the generated GYP actions.

Change-Id: Ic875a818ee0cda85efcb3ccebaf885872aed8746
Reviewed-by: Michael Bruning <michael.bruning@digia.com>
Reviewed-by: Jarred Nicholls <jarred.nicholls@gmail.com>