Fix isInternalProperty when there are no internal properties

Source/build/scripts/make_css_property_names.py

 #!/usr/bin/env python
 
 import subprocess
 import sys
 
 import css_properties
 import in_generator
 import license
 
 
@@ skipping 146 matching lines @@
             character = (propertyNamePointer - 2 != cssPropertyName) ? toASCIIUpper(nextCharacter) : nextCharacter;
         }
         *resultPointer++ = character;
     }
     *resultPointer = '\\0';
     return String(result);
 }
 
 bool isInternalProperty(CSSPropertyID id)
 {
-    switch (id) {
-        %(internal_properties)s
-            return true;
-        default:
-            return false;
-    }
+    %(internal_properties)s
 }
 
 } // namespace blink
 """
 
 
 class CSSPropertyNamesWriter(css_properties.CSSProperties):
     class_name = "CSSPropertyNames"
 
     def __init__(self, in_file_path):
@@ skipping 20 matching lines @@
         property_offsets = []
         current_offset = 0
         for property in self._properties_list:
             property_offsets.append(current_offset)
             current_offset += len(property["name"]) + 1
 
         css_name_and_enum_pairs = [(property['name'], property_id) for property_id, property in self._properties.items()]
         for name, aliased_name in self._aliases.items():
             css_name_and_enum_pairs.append((name, css_properties.css_name_to_enum(aliased_name)))
 
+        internal_properties = ""
+        internal_properties = '\n'.join("case %s:" % property_id for property_id, property in self._properties.items() if property['is_internal'])
+        if internal_properties:
+            internal_properties = "switch (id) {\n        " +\
+                                  internal_properties +\
+                                  "\n            return true;" +\
+                                  "\n        default:" +\
+                                  "\n            return false;" +\
+                                  "\n    }\n"
+        else:
+            internal_properties = "return false;"
+
         gperf_input = GPERF_TEMPLATE % {
             'license': license.license_for_generated_cpp(),
             'class_name': self.class_name,
             'property_name_strings': '\n'.join(map(lambda property: '    "%(name)s\\0"' % property, self._properties_list)),
             'property_name_offsets': '\n'.join(map(lambda offset: '    %d,' % offset, property_offsets)),
             'property_to_enum_map': '\n'.join(map(lambda property: '%s, %s' % property, css_name_and_enum_pairs)),
-            'internal_properties': '\n'.join("case %s:" % property_id for property_id, property in self._properties.items() if property['is_internal']),
+            'internal_properties': internal_properties,
         }
         # FIXME: If we could depend on Python 2.7, we would use subprocess.check_output
         gperf_args = [self.gperf_path, '--key-positions=*', '-P', '-n']
         gperf_args.extend(['-m', '50'])  # Pick best of 50 attempts.
         gperf_args.append('-D')  # Allow duplicate hashes -> More compact code.
         gperf = subprocess.Popen(gperf_args, stdin=subprocess.PIPE, stdout=subprocess.PIPE, universal_newlines=True)
         return gperf.communicate(gperf_input)[0]
 
 
 if __name__ == "__main__":
     in_generator.Maker(CSSPropertyNamesWriter).main(sys.argv)