Generate CSSPropertyEquality instead of using hand-updated file.

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 3ece896d5b1d88ae5190130c2cd272fcad8d4532..d92449ee00df5d5d2b614479495dea1c83377804 100644
--- a/third_party/WebKit/Source/core/BUILD.gn
+++ b/third_party/WebKit/Source/core/BUILD.gn
@@ -416,6 +416,10 @@ source_set("core_generated") {
 
     # Generated from make_cssom_keywords.py
     "$blink_core_output_dir/CSSOMKeywords.cpp",
+
+    # Generated from make_css_property_equality.py
+    "$blink_core_output_dir/CSSPropertyEquality.cpp",
+    "$blink_core_output_dir/CSSPropertyEqualityCustom.h",
   ]
 
   configs -= core_config_remove
@@ -565,6 +569,7 @@ action("generated_testing_idls_internal_runtime_flags") {
 group("make_core_generated") {
   public_deps = [
     ":make_core_generated_bison",
+    ":make_core_generated_css_property_equality",
     ":make_core_generated_css_property_metadata",
     ":make_core_generated_css_property_names",
     ":make_core_generated_css_tokenizer_codepoints",
@@ -662,6 +667,19 @@ css_properties("make_core_generated_cssom_types") {
   ]
 }
 
+# "CSSOMTypes" in make_core_generated from GYP.
+css_properties("make_core_generated_css_property_equality") {
+  script = "../build/scripts/make_css_property_equality.py"
+  other_inputs = [
+    "../build/scripts/templates/CSSPropertyEquality.cpp.tmpl",
+    "../build/scripts/templates/CSSPropertyEqualityCustom.h.tmpl",
+  ]
+  outputs = [
+    "$blink_core_output_dir/CSSPropertyEquality.cpp",
+    "$blink_core_output_dir/CSSPropertyEqualityCustom.h",
+  ]
+}
+
 # "CSSPropertyMetadata" in make_core_generated from GYP.
 css_properties("make_core_generated_css_property_metadata") {
   script = "../build/scripts/make_css_property_metadata.py"