Implement CSSPaintValue and add a layout test.

third_party/WebKit/Source/core/css/CSSPaintValue.cpp

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/css/CSSPaintValue.h"
 
 #include "core/css/CSSCustomIdentValue.h"
+#include "core/css/CSSSyntaxDescriptor.h"
+#include "core/css/cssom/StyleValueFactory.h"
 #include "core/layout/LayoutObject.h"
 #include "platform/graphics/Image.h"
 #include "wtf/text/StringBuilder.h"
 
 namespace blink {
 
 CSSPaintValue::CSSPaintValue(CSSCustomIdentValue* name)
     : CSSImageGeneratorValue(PaintClass),
       m_name(name),
       m_paintImageGeneratorObserver(new Observer(this)) {}
@@ skipping 22 matching lines @@
   return m_name->value();
 }
 
 PassRefPtr<Image> CSSPaintValue::image(const LayoutObject& layoutObject,
                                        const IntSize& size,
                                        float zoom) {
   if (!m_generator)
     m_generator = CSSPaintImageGenerator::create(
         name(), layoutObject.document(), m_paintImageGeneratorObserver);
 
-  return m_generator->paint(layoutObject, size, zoom);
+  if (m_inputArgumentsInValid)
+    return nullptr;
+
+  if (!m_parsedInputArguments) {
+    // Parse arguments.

[ikilpatrick, 2017/02/27 17:25:02]

Could you extract this into a private function, and just have:

if (!parseInputArguments())
  return nullptr;

bool CSSPaintValue::parseInputArguments() {
  if (somethingBad...) {
    return false;
  }

  return true;
}

[renjieliu1, 2017/02/27 23:20:43]

thanks for the suggestion

+    if (RuntimeEnabledFeatures::cssPaintAPIArgumentsEnabled()) {
+      if (!m_generator->isImageGeneratorReady()) {
+        return nullptr;
+      }
+      const Vector<CSSSyntaxDescriptor>& inputArgumentTypes =
+          m_generator->inputArgumentTypes();
+      if (m_argumentVariableData.size() != inputArgumentTypes.size()) {
+        m_inputArgumentsInValid = true;
+        return nullptr;
+      }
+
+      m_parsedInputArguments = new CSSStyleValueVector();
+
+      for (size_t i = 0; i < m_argumentVariableData.size(); ++i) {
+        const CSSValue* parsedValue =
+            m_argumentVariableData[i]->parseForSyntax(inputArgumentTypes[i]);
+        if (!parsedValue) {
+          m_inputArgumentsInValid = true;
+          m_parsedInputArguments = nullptr;
+          return nullptr;
+        }
+        m_parsedInputArguments->appendVector(
+            StyleValueFactory::cssValueToStyleValueVector(*parsedValue));
+      }
+    }
+  }
+
+  return m_generator->paint(layoutObject, size, zoom, m_parsedInputArguments);
 }
 
 void CSSPaintValue::Observer::paintImageGeneratorReady() {
   m_ownerValue->paintImageGeneratorReady();
 }
 
 void CSSPaintValue::paintImageGeneratorReady() {
   for (const LayoutObject* client : clients().keys()) {
     const_cast<LayoutObject*>(client)->imageChanged(
         static_cast<WrappedImagePtr>(this));
   }
 }
 
 bool CSSPaintValue::knownToBeOpaque(const LayoutObject& layoutObject) const {
   return m_generator && !m_generator->hasAlpha();
 }
 
 bool CSSPaintValue::equals(const CSSPaintValue& other) const {
   return name() == other.name() && customCSSText() == other.customCSSText();
 }
 
 DEFINE_TRACE_AFTER_DISPATCH(CSSPaintValue) {
   visitor->trace(m_name);
   visitor->trace(m_generator);
   visitor->trace(m_paintImageGeneratorObserver);
+  visitor->trace(m_parsedInputArguments);
   CSSImageGeneratorValue::traceAfterDispatch(visitor);
 }
 
 }  // namespace blink