Factor and simplify generation of the lookup trie used for HTMLLookupTrie.

third_party/WebKit/Source/build/scripts/scripts.gypi

 # The GN build definitions for these variables are in scripts.gni.
 {
     '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',
             'license.py',
             'name_utilities.py',
             'template_expander.py',
+            'trie_builder.py',
             'templates/macros.tmpl',
         ],
         'css_properties_files': [
             '<@(scripts_for_in_files)',
             'css_properties.py',
             '../../core/css/CSSProperties.in',
         ],
         'make_event_factory_files': [
             '<@(scripts_for_in_files)',
             'make_event_factory.py',
@@ skipping 15 matching lines @@
             '<@(make_qualified_names_files)',
             'make_element_factory.py',
             'templates/ElementFactory.cpp.tmpl',
             'templates/ElementFactory.h.tmpl',
         ],
         'make_element_type_helpers_files': [
             '<@(make_qualified_names_files)',
             'make_element_type_helpers.py',
             'templates/ElementTypeHelpers.h.tmpl',
         ],
+        'make_trie_helpers_files': [
+            '<@(scripts_for_in_files)',
+            'trie_builder.py', 
+        ],
         'conditions': [
             ['OS=="win"', {
                 'gperf_exe': '<(DEPTH)/third_party/gperf/bin/gperf.exe',
                 'bison_exe': '<(DEPTH)/third_party/bison/bin/bison.exe',
               },{
                 'gperf_exe': 'gperf',
                 'bison_exe': 'bison',
               }],
          ],
     },
 }