Merge .in files for css/svg properties into a single file

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_macros.py',
             'name_utilities.py',
             'template_expander.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',
             'templates/EventFactory.cpp.tmpl',
         ],
         'make_names_files': [
             '<@(scripts_for_in_files)',
             'make_names.py',
             'templates/MakeNames.cpp.tmpl',
             'templates/MakeNames.h.tmpl',
@@ skipping 21 matching lines @@
             ['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',
               }],
          ],
     },
 }