Exploit sharing when comparing and copying groups in ComputedStyle.

third_party/WebKit/Source/build/scripts/make_computed_style_base.py

Index: third_party/WebKit/Source/build/scripts/make_computed_style_base.py
diff --git a/third_party/WebKit/Source/build/scripts/make_computed_style_base.py b/third_party/WebKit/Source/build/scripts/make_computed_style_base.py
index 3bf2698081ab669e618a944a72fafdc8557b5a24..b52ab45c015cddf0ee10ad7f4a8b266460fa3d80 100755
--- a/third_party/WebKit/Source/build/scripts/make_computed_style_base.py
+++ b/third_party/WebKit/Source/build/scripts/make_computed_style_base.py
@@ -359,7 +359,7 @@ class ComputedStyleBaseWriter(make_style_builder.StyleBuilderWriter):
             'ComputedStyleBaseConstants.h': self.generate_base_computed_style_constants,
         }
 
-    @template_expander.use_jinja('ComputedStyleBase.h.tmpl')
+    @template_expander.use_jinja('ComputedStyleBase.h.tmpl', tests={'in': lambda a, b: a in b})
     def generate_base_computed_style_h(self):
         return {
             'properties': self._properties,
@@ -368,7 +368,7 @@ class ComputedStyleBaseWriter(make_style_builder.StyleBuilderWriter):
             'computed_style': self._root_group,
         }
 
-    @template_expander.use_jinja('ComputedStyleBase.cpp.tmpl')
+    @template_expander.use_jinja('ComputedStyleBase.cpp.tmpl', tests={'in': lambda a, b: a in b})
     def generate_base_computed_style_cpp(self):
         return {
             'properties': self._properties,