Support unset in CSSParserFastPaths

Support unset as a CSS wide keyword [1] and add some unit tests for it.

[1] https://www.w3.org/TR/css3-values/#common-keywords

Bug: 660273
Change-Id: Ic739055b83988017e11ff3968c1a0aad48073613
Reviewed-on: https://chromium-review.googlesource.com/663820
Commit-Queue: Rob Buis <rob.buis@samsung.com>
Reviewed-by: Bugs Nash <bugsnash@chromium.org>
Reviewed-by: meade_UTC10 <meade@chromium.org>
Cr-Commit-Position: refs/heads/master@{#501642}

third_party/WebKit/Source/core/css/parser/CSSParserFastPaths.cpp

@@ -12,6 +12,7 @@
 #include "core/css/CSSInheritedValue.h"
 #include "core/css/CSSInitialValue.h"
 #include "core/css/CSSPrimitiveValue.h"
+#include "core/css/CSSUnsetValue.h"
 #include "core/css/StyleColor.h"
 #include "core/css/parser/CSSParserIdioms.h"
 #include "core/css/parser/CSSPropertyParser.h"
@@ -985,12 +986,13 @@ static CSSValue* ParseKeywordValue(CSSPropertyID property_id,
   DCHECK(!string.IsEmpty());
 
   if (!CSSParserFastPaths::IsKeywordPropertyID(property_id)) {
-    // All properties accept the values of "initial" and "inherit".
+    // All properties accept the values of "initial," "inherit" and "unset".
     if (!EqualIgnoringASCIICase(string, "initial") &&
-        !EqualIgnoringASCIICase(string, "inherit"))
+        !EqualIgnoringASCIICase(string, "inherit") &&
+        !EqualIgnoringASCIICase(string, "unset"))
       return nullptr;
 
-    // Parse initial/inherit shorthands using the CSSPropertyParser.
+    // Parse initial/inherit/unset shorthands using the CSSPropertyParser.
     if (shorthandForProperty(property_id).length())
       return nullptr;
 
@@ -1008,6 +1010,8 @@ static CSSValue* ParseKeywordValue(CSSPropertyID property_id,
     return CSSInheritedValue::Create();
   if (value_id == CSSValueInitial)
     return CSSInitialValue::Create();
+  if (value_id == CSSValueUnset)
+    return CSSUnsetValue::Create();
   if (CSSParserFastPaths::IsValidKeywordPropertyAndValue(property_id, value_id,
                                                          parser_mode))
     return CSSIdentifierValue::Create(value_id);

third_party/WebKit/Source/core/css/parser/CSSParserFastPathsTest.cpp

@@ -24,7 +24,8 @@ TEST(CSSParserFastPathsTest, ParseKeyword) {
                                               kHTMLStandardMode);
   ASSERT_EQ(nullptr, value);
 }
-TEST(CSSParserFastPathsTest, ParseInitialAndInheritKeyword) {
+
+TEST(CSSParserFastPathsTest, ParseCSSWideKeywords) {
   CSSValue* value = CSSParserFastPaths::MaybeParseValue(
       CSSPropertyMarginTop, "inherit", kHTMLStandardMode);
   ASSERT_NE(nullptr, value);
@@ -41,6 +42,14 @@ TEST(CSSParserFastPathsTest, ParseInitialAndInheritKeyword) {
                                               kHTMLStandardMode);
   ASSERT_NE(nullptr, value);
   EXPECT_TRUE(value->IsInitialValue());
+  value = CSSParserFastPaths::MaybeParseValue(CSSPropertyMarginTop, "unset",
+                                              kHTMLStandardMode);
+  ASSERT_NE(nullptr, value);
+  EXPECT_TRUE(value->IsUnsetValue());
+  value = CSSParserFastPaths::MaybeParseValue(CSSPropertyMarginLeft, "unsEt",
+                                              kHTMLStandardMode);
+  ASSERT_NE(nullptr, value);
+  EXPECT_TRUE(value->IsUnsetValue());
   // Fast path doesn't handle short hands.
   value = CSSParserFastPaths::MaybeParseValue(CSSPropertyMargin, "initial",
                                               kHTMLStandardMode);