Fix isInternalProperty when there are no internal properties

Source/build/scripts/make_css_property_names.py

Index: Source/build/scripts/make_css_property_names.py
diff --git a/Source/build/scripts/make_css_property_names.py b/Source/build/scripts/make_css_property_names.py
index 530a1878d5a24714f3ef10880b785a7fa5a5908c..555e16ab876c9e8ddf87e9cd9e91a1c5ec9911b5 100755
--- a/Source/build/scripts/make_css_property_names.py
+++ b/Source/build/scripts/make_css_property_names.py
@@ -164,12 +164,7 @@ String getJSPropertyName(CSSPropertyID id)
 
 bool isInternalProperty(CSSPropertyID id)
 {
-    switch (id) {
-        %(internal_properties)s
-            return true;
-        default:
-            return false;
-    }
+    %(internal_properties)s
 }
 
 } // namespace blink
@@ -210,13 +205,25 @@ class CSSPropertyNamesWriter(css_properties.CSSProperties):
         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']