Generate isHTML*Element() / toHTML*Element() helper functions

Source/build/scripts/scripts.gypi

 {
     'variables': {
         'scripts_for_in_files': [
             # jinja2/__init__.py contains version string, so sufficient as
             # dependency for whole jinja2 package
             '<(DEPTH)/third_party/jinja2/__init__.py',
             '<(DEPTH)/third_party/markupsafe/__init__.py',  # jinja2 dep
             'hasher.py',
             'in_file.py',
             'in_generator.py',
@@ skipping 21 matching lines @@
             'templates/MakeQualifiedNames.h.tmpl',
         ],
         'make_element_factory_files': [
             '<@(make_qualified_names_files)',
             'make_element_factory.py',
             'templates/ElementFactory.cpp.tmpl',
             'templates/ElementFactory.h.tmpl',
             'templates/ElementWrapperFactory.cpp.tmpl',
             'templates/ElementWrapperFactory.h.tmpl',
         ],
+        'make_element_type_helpers_files': [
+            '<@(make_qualified_names_files)',
+            'make_element_type_helpers.py',
+            'templates/ElementTypeHelpers.h.tmpl',
+        ],
         'conditions': [
             ['OS=="win"', {
                 # Using native perl rather than cygwin perl cuts execution time
                 # of idl preprocessing rules by a bit more than 50%.
                 'perl_exe': '<(DEPTH)/third_party/perl/perl/bin/perl.exe',
                 'gperf_exe': '<(DEPTH)/third_party/gperf/bin/gperf.exe',
                 'bison_exe': '<(DEPTH)/third_party/bison/bin/bison.exe',
                 # Using cl instead of cygwin gcc cuts the processing time from
                 # 1m58s to 0m52s.
                 'preprocessor': '--preprocessor "cl.exe -nologo -EP -TP"',
               },{
                 'perl_exe': 'perl',
                 'gperf_exe': 'gperf',
                 'bison_exe': 'bison',
                 # We specify a preprocess so it happens locally and won't get
                 # distributed to goma.
                 # FIXME: /usr/bin/gcc won't exist on OSX forever. We want to
                 # use /usr/bin/clang once we require Xcode 4.x.
                 'preprocessor': '--preprocessor "/usr/bin/gcc -E -P -x c++"'
               }],
          ],
     },
 }