Add a generated ComputedStyleBase class that ComputedStyle extends

third_party/WebKit/Source/core/BUILD.gn

Index: third_party/WebKit/Source/core/BUILD.gn
diff --git a/third_party/WebKit/Source/core/BUILD.gn b/third_party/WebKit/Source/core/BUILD.gn
index 70c7179de57469f3c449a2ef7ced437b2daf540b..cf4efc96138d422093a33b12556a1bc12c8a1d91 100644
--- a/third_party/WebKit/Source/core/BUILD.gn
+++ b/third_party/WebKit/Source/core/BUILD.gn
@@ -369,6 +369,11 @@ target(link_target_type, "core_generated") {
   sources += generated_core_dictionary_files
 
   sources += [
+    # Generated from make_base_computed_style.py
+    "$blink_core_output_dir/BaseComputedStyle.cpp",
+    "$blink_core_output_dir/BaseComputedStyle.h",
+    "$blink_core_output_dir/BaseComputedStyleConstants.h",
+
     # Additional .cpp files for HashTools.h
     "$blink_core_output_dir/CSSPropertyNames.cpp",
     "$blink_core_output_dir/CSSValueKeywords.cpp",
@@ -615,6 +620,7 @@ action("generated_testing_idls_internal_runtime_flags") {
 # GYP version: WebKit/Source/core/core_generated.gyp:make_core_generated
 group("make_core_generated") {
   public_deps = [
+    ":make_core_generated_base_computed_style",
     ":make_core_generated_bison",
     ":make_core_generated_css_primitive_value_unit_trie",
     ":make_core_generated_css_property_metadata",
@@ -651,6 +657,21 @@ group("make_core_generated") {
   ]
 }
 
+# "BaseComputedStyle" in make_core_generated from GYP.
+css_properties("make_core_generated_base_computed_style") {
+  script = "../build/scripts/make_base_computed_style.py"
+  other_inputs = [
+    "../build/scripts/templates/BaseComputedStyle.cpp.tmpl",
+    "../build/scripts/templates/BaseComputedStyle.h.tmpl",
+    "../build/scripts/templates/BaseComputedStyleConstants.h.tmpl",
+  ]
+  outputs = [
+    "$blink_core_output_dir/BaseComputedStyle.cpp",
+    "$blink_core_output_dir/BaseComputedStyle.h",
+    "$blink_core_output_dir/BaseComputedStyleConstants.h",
+  ]
+}
+
 # "CSSPropertyNames" in make_core_generated from GYP.
 css_properties("make_core_generated_css_property_names") {
   script = "../build/scripts/make_css_property_names.py"