Exploit sharing when comparing and copying groups in ComputedStyle.

third_party/WebKit/Source/build/scripts/templates/ComputedStyleBase.cpp.tmpl

 {% from 'macros.tmpl' import license %}
-{% from 'fields/field.tmpl' import getter_expression, setter_expression %}
+{% from 'fields/field.tmpl' import getter_expression, setter_expression, fieldwise_copy %}
 {{license()}}
 
 #include "core/ComputedStyleBase.h"
 #include "platform/wtf/SizeAssertions.h"
 
 namespace blink {
 
 struct SameSizeAsComputedStyleBase {
   {% if computed_style.subgroups is defined %}
   void* dataRefs[{{computed_style.subgroups|length}}];
   {% endif %}
   {% for field in computed_style.fields|rejectattr("is_bit_field") %}
   {{field.type_name}} {{field.name}}};
   {% endfor %}
   unsigned m_bit_fields[{{computed_style.num_32_bit_words_for_bit_fields}}];
 };
 
 // If this fails, the packing algorithm in make_computed_style_base.py has
 // failed to produce the optimal packed size. To fix, update the algorithm to
 // ensure that the buckets are placed so that each takes up at most 1 word.
 ASSERT_SIZE(ComputedStyleBase, SameSizeAsComputedStyleBase);
 
-void ComputedStyleBase::InheritFrom(const ComputedStyleBase& inheritParent,
+void ComputedStyleBase::InheritFrom(const ComputedStyleBase& other,
                                     IsAtShadowBoundary isAtShadowBoundary) {
-  {% for field in computed_style.all_fields if field.is_inherited %}
-  {{setter_expression(field)}} = inheritParent.{{getter_expression(field)}};
-  {% endfor %}
+  {{fieldwise_copy(computed_style, computed_style.all_fields
+      |selectattr("is_inherited")
+      |list
+    )|indent(2)}}
 }
 
 void ComputedStyleBase::CopyNonInheritedFromCached(
     const ComputedStyleBase& other) {
-  {% for field in computed_style.all_fields if (field.is_property and not field.is_inherited) or field.is_inherited_flag %}
-  {{setter_expression(field)}} = other.{{getter_expression(field)}};
-  {% endfor %}
+  {{fieldwise_copy(computed_style, computed_style.all_fields
+      |rejectattr("is_nonproperty")
+      |rejectattr("is_inherited")
+      |list
+    )|indent(2)}}
 }
 
 void ComputedStyleBase::PropagateIndependentInheritedProperties(
     const ComputedStyleBase& parentStyle) {
   {% for field in computed_style.all_fields if field.is_property and field.is_independent %}
   if ({{field.is_inherited_method_name}}())
     {{setter_expression(field)}} = parentStyle.{{getter_expression(field)}};
   {% endfor %}
 }
 
 } // namespace blink