[WIP] CSS Motion Path: offset shorthand ready for position and anchor

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

Index: third_party/WebKit/Source/core/css/parser/CSSPropertyParser.cpp
diff --git a/third_party/WebKit/Source/core/css/parser/CSSPropertyParser.cpp b/third_party/WebKit/Source/core/css/parser/CSSPropertyParser.cpp
index 6ec988e3340bcecb4ff4d129cd760f1312259d5b..2e9ccec8b4cba2c3a6b4c3ff85ab82d8e6383127 100644
--- a/third_party/WebKit/Source/core/css/parser/CSSPropertyParser.cpp
+++ b/third_party/WebKit/Source/core/css/parser/CSSPropertyParser.cpp
@@ -1562,6 +1562,56 @@ CSSValue* consumeOffsetPosition(CSSParserTokenRange& range, CSSParserMode cssPar
     return consumePosition(range, cssParserMode, UnitlessQuirk::Forbid);
 }
 
+bool CSSPropertyParser::consumeOffsetShorthand(bool important)
+{
+    const CSSValue* offsetPosition = consumeOffsetPosition(m_range, m_context.mode());
+    const CSSValue* offsetPath = consumePathOrNone(m_range);
+
+    // If offsetPath is omitted, offsetPosition must be present, and must not be 'auto'
+    if (!offsetPath && (!offsetPosition || !offsetPosition->isValuePair()))
+        return false;
+
+    const CSSValue* offsetRotation = consumeOffsetRotation(m_range);
+    const CSSValue* offsetDistance = nullptr;
+    if (offsetPath) {
+        offsetDistance = consumeLengthOrPercent(m_range, m_context.mode(), ValueRangeAll);
+        if (offsetDistance && !offsetRotation)
+            offsetRotation = consumeOffsetRotation(m_range);
+    }
+    const CSSValue* offsetAnchor = nullptr;
+    if (consumeSlashIncludingWhitespace(m_range)) {
+        offsetAnchor = consumeOffsetPosition(m_range, m_context.mode());
+        if (!offsetAnchor)
+            return false;
+    }
+
+    if (RuntimeEnabledFeatures::cssOffsetPositionAnchorEnabled()) {
+        addProperty(CSSPropertyOffsetPosition, CSSPropertyOffset, offsetPosition ? *offsetPosition : *CSSPrimitiveValue::createIdentifier(CSSValueAuto), important);
+
+        if (!offsetAnchor) {
+            CSSPrimitiveValue* fiftyPercent = CSSPrimitiveValue::create(50, CSSPrimitiveValue::UnitType::Percentage);
+            offsetAnchor = CSSValuePair::create(fiftyPercent, fiftyPercent, CSSValuePair::KeepIdenticalValues);
+        }
+        addProperty(CSSPropertyOffsetAnchor, CSSPropertyOffset, *offsetAnchor, important);
+    } else if (offsetPosition || offsetAnchor) {
+        // We could report a console warning "offset-position and offset-anchor are not yet supported."
+        return false;
+    }
+
+    addProperty(CSSPropertyOffsetPath, CSSPropertyOffset, offsetPath ? *offsetPath : *CSSPrimitiveValue::createIdentifier(CSSValueNone), important);
+
+    addProperty(CSSPropertyOffsetDistance, CSSPropertyOffset, offsetDistance ? *offsetDistance : *CSSPrimitiveValue::create(0, CSSPrimitiveValue::UnitType::Pixels), important);
+
+    if (!offsetRotation) {
+        CSSValueList* list = CSSValueList::createSpaceSeparated();
+        list->append(*CSSPrimitiveValue::createIdentifier(CSSValueAuto));
+        offsetRotation = list;
+    }
+    addProperty(CSSPropertyOffsetRotation, CSSPropertyOffset, *offsetRotation, important);
+
+    return m_range.atEnd();
+}
+
 static CSSValue* consumeTextEmphasisStyle(CSSParserTokenRange& range)
 {
     CSSValueID id = range.peek().id();
@@ -4664,7 +4714,7 @@ bool CSSPropertyParser::parseShorthand(CSSPropertyID unresolvedProperty, bool im
     case CSSPropertyMotion:
         return consumeShorthandGreedily(motionShorthand(), important);
     case CSSPropertyOffset:
-        return consumeShorthandGreedily(offsetShorthand(), important);
+        return consumeOffsetShorthand(important);
     case CSSPropertyWebkitTextEmphasis:
         return consumeShorthandGreedily(webkitTextEmphasisShorthand(), important);
     case CSSPropertyOutline: